I've been using backtrack4 beta for a while on a 8GB usb flash drive. I used the following tut to get a persistent changes option going: (just add the www) infosecramblings.com/backtrack/backtrack-4-usbpersistent-changesnessus/
I have the 2nd partition with a changes folder and edited the syslinux.cfg and added the changes=/dev/sdx2.
It worked perfectly: no problems and I've used it over a month now. I have installed/updated a boat load of programs and now would like to merge my persistent changes into an .iso and have that be my live usb default boot. That way I can use that as I pentest so as not to potentially screw anything up with my good (persistent build). I've searched all over (and I of course could be a moron so forgive me if this ticks any of you off) but haven't found anything with my specific situation. I am guessing it would be a bit faster that way as well since instead of reading off the main partition then also going to the 2nd partition it would just go off the one. The new backtrack 4 wiki has a how-to on creating your own custom .iso but that is from scratch and using vmware. Since I've already put alot of time getting my current image I'd hate to have to start all over again. Thanks for anyone pointing me in the right direction.