[Nvidia Tegra Note 7] mike-s:
I didn't have any luck doing it this way. I ended up getting there by a slightly different avenue.

My s7e was totally non functional beyong fastboot and recovery mode being operational. I ended up downloading tegratools 2.2. Using the fastboot included in that I unlocked my boot loader with fastboot by the command

fastboot -i 0x03F0 oem unlock

(The '-i 0x03F0' is a code relating to the specific model, apparently without this the tablet will ignore your command. Please also remember that the unlock factory resets the tablet.)

It may be overboard again, but I also formatted all the system partitions

fastboot -i 0x03F0 erase boot
fastboot -i 0x03F0 erase system
fastboot -i 0x03F0 erase userdata
fastboot -i 0x03F0 erase cache
fastboot -i 0x03F0 erase preinstall
fastboot -i 0x03F0 reboot

I uploaded cwm recovery from the above version of tegratools to my s7e as it seems a bit more forgiving with signatures than the stock recovery. I used that to upload a version of update.zip with the "assert" lines removed from META-INF\com\google\android\updater-script. I also self signed the .zip to reduce the likelyhood of my upload being rejected by the tablet, it may not be needed, but I did it anyway.

adb sideload slate7update-signed.zip

when completing the firmware flash, apparently there is a common problem of the kernel not flashing correctly when recovery takes place and giving an "Error 7", this is the problem I think you solved by re-writing the unmodified firmware (but that didn't work for me)

Anyway I had to fix it by dropping back to fastboot and flashing it to "staging", which puts the kernel in a placeholder until the next boot, at which point the kernel will be written to the correct spot. Because of this writing to the correct partition, you will notice a quick double-boot as the updated kernel is written to the correct point in firmware.

fastboot -i 0x03F0 flash staging "c:\fastboot-s7e\blob"

I hope this helps.

Oh and to those curious, the beats version appears incompatible with the standard s7e, I tried modifying a rom in the same way as above and it just went to a blank screen. My guess is they've done some form of sanity check in the kernel, given that every "beats" version I've read about in tablets has been a software-only modification. I've not bothered trying to use the beats version rom with the s7e kernel, I'll leave that for someone else to try in greater depth as I'm just happy that I got everything working again.

references:

Fastboot (previously this): This is a copy of the twrp/cwm roms as well as fastboot & adb taken from tegratools 2.2 mentioned above.

SignApk (Previously this): The java files and self signing certificate I used to sign the .zip file. It was actually a bit of a pain to find a working signapk.jar that had the valid certificates included, most were broken in one way or another when trying to sign on ubuntu 12.04.

slate7update-signed.zip (previously this): A signed copy of update.zip with META-INF\com\google\android\updater-script modified to remove the assert validation lines sanity checks, be careful with this, you could nuke your tablet if you use it on an incompatible bit of hardware.

guide.txt (previously this): A full how-to with a number of things I've omitted from this response.

To those wondering, I collated the above procedure from a dozen different links on a good four or five websites, including a number of threads here on XDA. Thank you to anyone out there that contributed to the information I found, you really made my day so much better in being able to recover my tablet.