Thanks, yes, I ended up figuring out how to activate USB boot with your other script via adb. I'm not going to use your gingerbread image in the end, because I could not get wifi and bluetooth to work... probably some weird compatibility thing with my USB wifi stick.
Still, if anyone else wants to try it, it seemed to work quite well.
Be careful with the adb scribt though, I'm still trying to re-enable booting from nand or micro-sd, I can only boot from usb for now, not really sure what I did there...