[HD2 Windows Mobile 6.5 ROM Development] sakajati:
Radio is already included in the rom, not sure though which one is the best. You can try any HSPL, let me know if you found any difference. I'm currently using 1.42 HSPL.

FYI all apps cooked into the rom will goes into the \windows folder, this is ok with OEM/OS package since these apps can run directly from \windows folder. But almost all 3rd party apps usually installs into the \Program Files folder just like PC apps. So you'll get duplicate/redundant files if we cook in for example Opera Browser. Take a look at this initflashfiles snippet:

Directory("\Windows\Opera9\profile"):-File("axobjects.ini","\Windows\axobjects.ini")
Directory("\Windows\Opera9\profile"):-File("encoding.bin","\Windows\encoding.bin")
Directory("\Windows\Opera9\profile"):-File("html40_entities.dtd","\Windows\html40_entities.dtd")
Directory("\Windows\Opera9\profile"):-File("input.ini","\Windows\input.ini")
Directory("\Windows\Opera9\profile"):-File("svg_mono.dat","\Windows\svg_mono.dat")
Directory("\Windows\Opera9\profile"):-File("svg_serif.dat","\Windows\svg_serif.dat")
Directory("\Windows\Opera9\profile"):-File("svg_ss.dat","\Windows\svg_ss.dat")
Directory("\Windows\Opera9\profile"):-File("svg-mo.dat","\Windows\svg-mo.dat")
Directory("\Windows\Opera9\profile"):-File("svg-mobd.dat","\Windows\svg-mobd.dat")
Directory("\Windows\Opera9\profile"):-File("svg-moit.dat","\Windows\svg-moit.dat")
Directory("\Windows\Opera9\profile"):-File("svg-sa.dat","\Windows\svg-sa.dat")
Directory("\Windows\Opera9\profile"):-File("svg-sabd.dat","\Windows\svg-sabd.dat")
Directory("\Windows\Opera9\profile"):-File("svg-se.dat","\Windows\svg-se.dat")
Directory("\Windows\Opera9\profile"):-File("svg-sebd.dat","\Windows\svg-sebd.dat")
Directory("\Windows\Opera9\profile"):-File("svg-ssit.dat","\Windows\svg-ssit.dat")
Directory("\Windows\Opera9\profile"):-File("browser.js","\Windows\browser.js")
Directory("\Windows\Opera9\profile"):-File("wml1_entities.dtd","\Windows\wml1_entities.dtd")
Directory("\Windows\Opera9\profile"):-File("xmlentities.ini","\Windows\xmlentities.ini")
Directory("\Windows\Opera9\profile"):-File("user.js","\Windows\user.js")

Directory("\Windows\Opera9\profile\help\imgcss"):-File("bullet.gif","\Windows\bullet.gif")
Directory("\Windows\Opera9\profile\help\imgcss"):-File("help.css","\Windows\help.css")
Directory("\Windows\Opera9\profile\help\imgcss"):-File("logo.png","\Windows\logo.png")
Directory("\Windows\Opera9\profile\help\imgcss"):-File("top_pattern.png","\Windows\top_pattern.png")

Directory("\Windows\Opera9\profile\images"):-File("arrow.png","\Windows\arrow.png")
Directory("\Windows\Opera9\profile\images"):-File("beam.png","\Windows\beam.png")
Directory("\Windows\Opera9\profile\images"):-File("blank.gif","\Windows\blank.gif")
Directory("\Windows\Opera9\profile\images"):-File("cross.png","\Windows\cross.png")
Directory("\Windows\Opera9\profile\images"):-File("delete.png","\Windows\delete.png")
Directory("\Windows\Opera9\profile\images"):-File("drive.gif","\Windows\drive.gif")
Directory("\Windows\Opera9\profile\images"):-File("error.png","\Windows\error.png")
Directory("\Windows\Opera9\profile\images"):-File("file.gif","\Windows\file.gif")
Directory("\Windows\Opera9\profile\images"):-File("folder.gif","\Windows\folder.gif")
Directory("\Windows\Opera9\profile\images"):-File("forward.png","\Windows\forward.png")
Directory("\Windows\Opera9\profile\images"):-File("hand.png","\Windows\hand.png")
Directory("\Windows\Opera9\profile\images"):-File("info.png","\Windows\info.png")
Directory("\Windows\Opera9\profile\images"):-File("link.gif","\Windows\link.gif")
Directory("\Windows\Opera9\profile\images"):-File("move.png","\Windows\move.png")
Directory("\Windows\Opera9\profile\images"):-File("oom.png","\Windows\oom.png")
Directory("\Windows\Opera9\profile\images"):-File("open.png","\Windows\open.png")
Directory("\Windows\Opera9\profile\images"):-File("opwidget.ico","\Windows\opwidget.ico")
Directory("\Windows\Opera9\profile\images"):-File("question.png","\Windows\question.png")
Directory("\Windows\Opera9\profile\images"):-File("reload.png","\Windows\reload.png")
Directory("\Windows\Opera9\profile\images"):-File("stop.png","\Windows\stop.png")
Directory("\Windows\Opera9\profile\images"):-File("trash.png","\Windows\trash.png")
Directory("\Windows\Opera9\profile\images"):-File("wait.png","\Windows\wait.png")
Directory("\Windows\Opera9\profile\images"):-File("warning.png","\Windows\warning.png")

Directory("\Windows\Opera9\profile\locale"):-File("search.ini","\Windows\search.ini")

Directory("\Windows\Opera9\profile\Settings"):-File("settings.html","\Windows\settings.html")

Directory("\Windows\Opera9\profile\Settings\Imgs"):-File("bar_closed.png","\Windows\bar_closed.png")
Directory("\Windows\Opera9\profile\Settings\Imgs"):-File("bar_open.png","\Windows\bar_open.png")
Directory("\Windows\Opera9\profile\Settings\Imgs"):-File("list_btn.png","\Windows\list_btn.png")
Directory("\Windows\Opera9\profile\Settings\Imgs"):-File("txt_fld.png","\Windows\txt_fld.png")

Directory("\Windows\Opera9\profile\skin"):-File("standard_skin.zip","\Windows\standard_skin.zip")

Directory("\Windows\Opera9\profile\styles"):-File("about.css","\Windows\about.css")
Directory("\Windows\Opera9\profile\styles"):-File("cache.css","\Windows\cache.css")
Directory("\Windows\Opera9\profile\styles"):-File("certinfo.css","\Windows\certinfo.css")
Directory("\Windows\Opera9\profile\styles"):-File("config.css","\Windows\config.css")
Directory("\Windows\Opera9\profile\styles"):-File("dir.css","\Windows\dir.css")
Directory("\Windows\Opera9\profile\styles"):-File("drives.css","\Windows\drives.css")
Directory("\Windows\Opera9\profile\styles"):-File("error.css","\Windows\error.css")
Directory("\Windows\Opera9\profile\styles"):-File("history.css","\Windows\history.css")
Directory("\Windows\Opera9\profile\styles"):-File("info.css","\Windows\info.css")
Directory("\Windows\Opera9\profile\styles"):-File("mime.css","\Windows\mime.css")
Directory("\Windows\Opera9\profile\styles"):-File("plugins.css","\Windows\plugins.css")
Directory("\Windows\Opera9\profile\styles"):-File("wml.css","\Windows\wml.css")

Directory("\Windows\Opera9\profile\styles\images"):-File("88c.png","\Windows\88c.png")
Directory("\Windows\Opera9\profile\styles\images"):-File("bar.png","\Windows\bar.png")
Directory("\Windows\Opera9\profile\styles\images"):-File("center.png","\Windows\center.png")
Directory("\Windows\Opera9\profile\styles\images"):-File("folder.gif","\Windows\folder.gif")
Directory("\Windows\Opera9\profile\styles\images"):-File("opera.png","\Windows\opera.png")
Directory("\Windows\Opera9\profile\styles\images"):-File("root.png","\Windows\root.png")
Directory("\Windows\Opera9\profile\styles\images"):-File("top.png","\Windows\top.png")

Directory("\Windows\Opera9\profile\styles\user"):-File("accessibility.css","\Windows\accessibility.css")
Directory("\Windows\Opera9\profile\styles\user"):-File("contrastbw.css","\Windows\contrastbw.css")
Directory("\Windows\Opera9\profile\styles\user"):-File("contrastwb.css","\Windows\contrastwb.css")
Directory("\Windows\Opera9\profile\styles\user"):-File("debugwithoutline.css","\Windows\debugwithoutline.css")
Directory("\Windows\Opera9\profile\styles\user"):-File("disabletables.css","\Windows\disabletables.css")
Directory("\Windows\Opera9\profile\styles\user"):-File("hidecertainsizes.css","\Windows\hidecertainsizes.css")
Directory("\Windows\Opera9\profile\styles\user"):-File("hidenonlinkimages.css","\Windows\hidenonlinkimages.css")
Directory("\Windows\Opera9\profile\styles\user"):-File("imageandlinkonly.css","\Windows\imageandlinkonly.css")
Directory("\Windows\Opera9\profile\styles\user"):-File("nostalgia.css","\Windows\nostalgia.css")
Directory("\Windows\Opera9\profile\styles\user"):-File("showstructure.css","\Windows\showstructure.css")
Directory("\Windows\Opera9\profile\styles\user"):-File("textonly.css","\Windows\textonly.css")
Directory("\Windows\Opera9\profile\styles\user"):-File("userstyle.ini","\Windows\userstyle.ini")

all of these files will be copied (since you can't delete/move files cooked in a rom) on initial setup from \windows folder to another folder. As you can see we'll get tons of redundant files. So if we must cook a 3rd party app like this, then better to cook it as a cab just like I did in this rom for Google Maps, Jbed, etc. SE xperia rom also use this method.

Having more files in \windows folder make device slower, but as tkalli said you might would not notice the difference. However I prefer to keep the rom 'clean' and as fast as possible.

Thanks mate :)