[Galaxy Tab 8.9 SGH-i957 Android Development] Scarchunk:
Yes, clear data/factory reset does appear to work fine via CWM.

Tried PM'ing this to you but stupid character limit wouldn't allow. Here is one of the numerous variations of scripts that I've tried to flash a custom rom with, all resulting in bootloop. I can break out most all the individual pieces of this script and they work just fine.

I've tried reordering the steps, different wipe/format/delete methods for clearing the existing system. Gotten rid the ui progress crap. Tried using system wiping binaries. Manually wiping data and/or installing kernel after flash. I've even tried copying other people's known working scripts and just changing the filesystem mount points with no luck. All resulting in a bootloop. I can paste some of the other script variations I've tried if that would be useful, but the idea is same across the board: wipe current rom, install new system, set permissions/symlinks, install kernel, and done...

ui_print(" ");
ui_print("**************************************");
ui_print("* Welcome to EarlROM *");
ui_print("**************************************");
ui_print(" ");

ui_print("Mounting system...");
mount("ext4", "EMMC", "/dev/block/mmcblk0p24", "/system");
ui_print(" ");

ui_print("Extracting temporary files...");
package_extract_dir("updates", "/tmp");
ui_print(" ");

ui_print("Wiping System...");
delete_recursive("/system");
delete_recursive("/cache");
delete_recursive("/data/dalvik-cache");
ui_print(" ");

ui_print("Installing System...");
package_extract_dir("system", "/system");
ui_print(" ");

ui_print("Creating Symlinks and Setting Permissions...");
ui_print(" ");

symlink("debuggerd", "/system/bin/csview");
symlink("dumpstate", "/system/bin/dumpmesg");
symlink("mksh", "/system/bin/sh");
symlink("toolbox", "/system/bin/cat", "/system/bin/chmod",
"/system/bin/chown", "/system/bin/cmp", "/system/bin/date",
"/system/bin/dd", "/system/bin/df", "/system/bin/dmesg",
"/system/bin/getevent",	"/system/bin/getprop", "/system/bin/hd",
"/system/bin/id", "/system/bin/ifconfig", "/system/bin/iftop",
"/system/bin/insmod", "/system/bin/ioctl", "/system/bin/ionice",
"/system/bin/kill", "/system/bin/ln", "/system/bin/log",
"/system/bin/ls", "/system/bin/lsmod", "/system/bin/lsof",
"/system/bin/mkdir", "/system/bin/mkdosfs", "/system/bin/mount",
"/system/bin/mv", "/system/bin/nandread", "/system/bin/netstat",
"/system/bin/newfs_msdos", "/system/bin/notify", "/system/bin/printenv",
"/system/bin/ps", "/system/bin/renice", "/system/bin/rm",
"/system/bin/rmdir", "/system/bin/rmmod", "/system/bin/route",
"/system/bin/schedtop",	"/system/bin/sendevent", "/system/bin/setconsole",
"/system/bin/setprop", "/system/bin/sleep", "/system/bin/smd",
"/system/bin/start", "/system/bin/stop", "/system/bin/sync",
"/system/bin/top", "/system/bin/umount", "/system/bin/uptime",
"/system/bin/vmstat", "/system/bin/watchprops", "/system/bin/wipe");
symlink("../xbin/busybox", "/system/bin/busybox");
symlink("../xbin/su", "/system/bin/su");
symlink("busybox", "/system/xbin/[", "/system/xbin/[[",
"/system/xbin/addgroup", "/system/xbin/adduser", "/system/xbin/adjtimex",
"/system/xbin/ar", "/system/xbin/arp", "/system/xbin/arping",
"/system/xbin/ash", "/system/xbin/awk", "/system/xbin/basename",
"/system/xbin/bbconfig", "/system/xbin/beep", "/system/xbin/blkid",
"/system/xbin/brctl", "/system/xbin/bunzip2", "/system/xbin/bzcat",
"/system/xbin/bzip2", "/system/xbin/cal", "/system/xbin/cat",
"/system/xbin/catv", "/system/xbin/chat", "/system/xbin/chattr",
"/system/xbin/chgrp", "/system/xbin/chmod", "/system/xbin/chown",
"/system/xbin/chpasswd", "/system/xbin/chpst", "/system/xbin/chroot",
"/system/xbin/chrt", "/system/xbin/chvt", "/system/xbin/cksum",
"/system/xbin/clear", "/system/xbin/cmp", "/system/xbin/comm",
"/system/xbin/cp", "/system/xbin/cpio", "/system/xbin/crond",
"/system/xbin/crontab", "/system/xbin/cryptpw", "/system/xbin/cttyhack",
"/system/xbin/cut", "/system/xbin/date", "/system/xbin/dc",
"/system/xbin/dd", "/system/xbin/deallocvt", "/system/xbin/delgroup",
"/system/xbin/deluser", "/system/xbin/depmod", "/system/xbin/devmem",
"/system/xbin/df", "/system/xbin/diff", "/system/xbin/dirname",
"/system/xbin/dmesg", "/system/xbin/dnsd", "/system/xbin/dnsdomainname",
"/system/xbin/dos2unix", "/system/xbin/du", "/system/xbin/dumpkmap",
"/system/xbin/echo", "/system/xbin/ed", "/system/xbin/egrep",
"/system/xbin/eject", "/system/xbin/env", "/system/xbin/envdir",
"/system/xbin/envuidgid", "/system/xbin/ether-wake", "/system/xbin/expand",
"/system/xbin/expr", "/system/xbin/fakeidentd", "/system/xbin/false",
"/system/xbin/fbset", "/system/xbin/fbsplash", "/system/xbin/fdflush",
"/system/xbin/fdformat", "/system/xbin/fdisk", "/system/xbin/fgrep",
"/system/xbin/find", "/system/xbin/findfs", "/system/xbin/fold",
"/system/xbin/free", "/system/xbin/fsck", "/system/xbin/fsck.minix",
"/system/xbin/fsync", "/system/xbin/ftpd", "/system/xbin/ftpget",
"/system/xbin/ftpput", "/system/xbin/fuser", "/system/xbin/getopt",
"/system/xbin/getty", "/system/xbin/grep", "/system/xbin/gunzip",
"/system/xbin/gzip", "/system/xbin/halt", "/system/xbin/hd",
"/system/xbin/hdparm", "/system/xbin/head", "/system/xbin/hexdump",
"/system/xbin/hostid", "/system/xbin/hostname", "/system/xbin/httpd",
"/system/xbin/hush", "/system/xbin/hwclock", "/system/xbin/id",
"/system/xbin/ifconfig", "/system/xbin/ifdown", "/system/xbin/ifenslave",
"/system/xbin/ifplugd", "/system/xbin/ifup", "/system/xbin/inetd",
"/system/xbin/init", "/system/xbin/insmod", "/system/xbin/install",
"/system/xbin/ionice", "/system/xbin/ip", "/system/xbin/ipaddr",
"/system/xbin/ipcalc", "/system/xbin/ipcrm", "/system/xbin/ipcs",
"/system/xbin/iplink", "/system/xbin/iproute", "/system/xbin/iprule",
"/system/xbin/iptunnel", "/system/xbin/kbd_mode", "/system/xbin/kill",
"/system/xbin/killall", "/system/xbin/killall5", "/system/xbin/klogd",
"/system/xbin/last", "/system/xbin/length", "/system/xbin/less",
"/system/xbin/linux32", "/system/xbin/linux64", "/system/xbin/linuxrc",
"/system/xbin/ln", "/system/xbin/loadfont", "/system/xbin/loadkmap",
"/system/xbin/logger", "/system/xbin/login", "/system/xbin/logname",
"/system/xbin/logread", "/system/xbin/losetup", "/system/xbin/lpd",
"/system/xbin/lpq", "/system/xbin/lpr", "/system/xbin/ls",
"/system/xbin/lsattr", "/system/xbin/lsmod", "/system/xbin/lzmacat",
"/system/xbin/lzop", "/system/xbin/lzopcat", "/system/xbin/makedevs",
"/system/xbin/makemime", "/system/xbin/man", "/system/xbin/md5sum",
"/system/xbin/mdev", "/system/xbin/mesg", "/system/xbin/microcom",
"/system/xbin/mkdir", "/system/xbin/mkdosfs", "/system/xbin/mkfifo",
"/system/xbin/mkfs.minix", "/system/xbin/mkfs.vfat", "/system/xbin/mknod",
"/system/xbin/mkpasswd", "/system/xbin/mkswap", "/system/xbin/mktemp",
"/system/xbin/modprobe", "/system/xbin/more", "/system/xbin/mount",
"/system/xbin/mountpoint", "/system/xbin/msh", "/system/xbin/mt",
"/system/xbin/mv", "/system/xbin/nameif", "/system/xbin/nc",
"/system/xbin/netstat", "/system/xbin/nice", "/system/xbin/nmeter",
"/system/xbin/nohup", "/system/xbin/nslookup", "/system/xbin/od",
"/system/xbin/openvt", "/system/xbin/passwd", "/system/xbin/patch",
"/system/xbin/pgrep", "/system/xbin/pidof", "/system/xbin/ping",
"/system/xbin/ping6", "/system/xbin/pipe_progress", "/system/xbin/pivot_root",
"/system/xbin/pkill", "/system/xbin/popmaildir", "/system/xbin/poweroff",
"/system/xbin/printenv", "/system/xbin/printf", "/system/xbin/ps",
"/system/xbin/pscan", "/system/xbin/pwd", "/system/xbin/raidautorun",
"/system/xbin/rdate", "/system/xbin/rdev", "/system/xbin/readahead",
"/system/xbin/readlink", "/system/xbin/readprofile", "/system/xbin/realpath",
"/system/xbin/reformime", "/system/xbin/renice", "/system/xbin/reset",
"/system/xbin/resize", "/system/xbin/rm", "/system/xbin/rmdir",
"/system/xbin/rmmod", "/system/xbin/route", "/system/xbin/rtcwake",
"/system/xbin/run-parts", "/system/xbin/runlevel", "/system/xbin/runsv",
"/system/xbin/runsvdir", "/system/xbin/rx", "/system/xbin/script",
"/system/xbin/scriptreplay", "/system/xbin/sed", "/system/xbin/sendmail",
"/system/xbin/seq", "/system/xbin/setarch", "/system/xbin/setconsole",
"/system/xbin/setfont", "/system/xbin/setkeycodes", "/system/xbin/setlogcons",
"/system/xbin/setsid", "/system/xbin/setuidgid", "/system/xbin/sh",
"/system/xbin/sha1sum", "/system/xbin/sha256sum", "/system/xbin/sha512sum",
"/system/xbin/showkey", "/system/xbin/slattach", "/system/xbin/sleep",
"/system/xbin/softlimit", "/system/xbin/sort", "/system/xbin/split",
"/system/xbin/start-stop-daemon", "/system/xbin/stat", "/system/xbin/strings",
"/system/xbin/stty", "/system/xbin/sulogin", "/system/xbin/sum",
"/system/xbin/sv", "/system/xbin/svlogd", "/system/xbin/swapoff",
"/system/xbin/swapon", "/system/xbin/switch_root", "/system/xbin/sync",
"/system/xbin/sysctl", "/system/xbin/syslogd", "/system/xbin/tac",
"/system/xbin/tail", "/system/xbin/tar", "/system/xbin/tcpsvd",
"/system/xbin/tee", "/system/xbin/telnet", "/system/xbin/telnetd",
"/system/xbin/test", "/system/xbin/tftp", "/system/xbin/tftpd",
"/system/xbin/time", "/system/xbin/timeout", "/system/xbin/top",
"/system/xbin/touch", "/system/xbin/tr", "/system/xbin/traceroute",
"/system/xbin/true", "/system/xbin/tty", "/system/xbin/ttysize",
"/system/xbin/tunctl", "/system/xbin/udpsvd", "/system/xbin/umount",
"/system/xbin/uname", "/system/xbin/uncompress", "/system/xbin/unexpand",
"/system/xbin/uniq", "/system/xbin/unix2dos", "/system/xbin/unlzma",
"/system/xbin/unlzop", "/system/xbin/unzip", "/system/xbin/uptime",
"/system/xbin/usleep", "/system/xbin/uudecode", "/system/xbin/uuencode",
"/system/xbin/vconfig", "/system/xbin/vi", "/system/xbin/vlock",
"/system/xbin/volname", "/system/xbin/watch", "/system/xbin/watchdog",
"/system/xbin/wc", "/system/xbin/wget", "/system/xbin/which",
"/system/xbin/who", "/system/xbin/whoami", "/system/xbin/xargs",
"/system/xbin/yes", "/system/xbin/zcat", "/system/xbin/zcip");
set_perm_recursive(0, 0, 0755, 0644, "/system");
set_perm_recursive(0, 2000, 0755, 0755, "/system/bin");
set_perm(0, 3003, 02750, "/system/bin/netcfg");
set_perm(0, 3004, 02755, "/system/bin/ping");
set_perm(0, 2000, 06750, "/system/bin/run-as");
set_perm_recursive(1002, 1002, 0755, 0440, "/system/etc/bluetooth");
set_perm(0, 0, 0755, "/system/etc/bluetooth");
set_perm(1000, 1000, 0640, "/system/etc/bluetooth/auto_pairing.conf");
set_perm(3002, 3002, 0444, "/system/etc/bluetooth/blacklist.conf");
set_perm(1002, 1002, 0440, "/system/etc/dbus.conf");
set_perm(1014, 2000, 0550, "/system/etc/dhcpcd/dhcpcd-run-hooks");
set_perm_recursive(0, 2000, 0755, 0755, "/system/etc/init.d");
set_perm(0, 2000, 0550, "/system/etc/init.goldfish.sh");
set_perm_recursive(0, 0, 0755, 0555, "/system/etc/ppp");
set_perm_recursive(1000, 1000, 0775, 0644, "/system/etc/security");
set_perm_recursive(0, 2000, 0755, 0644, "/system/vendor");
set_perm(0, 0, 0644, "/system/vendor/lib/libmpu.so");
set_perm_recursive(0, 2000, 0755, 0755, "/system/xbin");
set_perm(0, 0, 04755, "/system/xbin/busybox");
set_perm(0, 0, 0755, "/system/xbin/remount");
set_perm(0, 0, 06755, "/system/xbin/su");
set_perm(0, 0, 06755, "/system/xbin/tcpdump");
set_perm(0, 0, 04755, "/system/xbin/zipalign");

ui_print("Flashing Kernel");
write_raw_image("/tmp/boot.img", "/dev/block/mmcblk0p8");
delete("/tmp/boot.img");
ui_print("");

ui_print("Unmounting...");
run_program("/sbin/cp", "/tmp/recovery.log", "/data/media/recovery.log");
unmount("/system");
unmount("/cache");
unmount("/data");
ui_print(" ");

ui_print("**************************************");
ui_print("* Enjoy! *");
ui_print("**************************************");

Earl's my dog's name BTW.