a couple words of caution for those working on ps3 flash.
first of all, writing to flash is possible with couple tools, personally i use dev_blind that allows ftp access with read/write (root) to flash0.
i prefer testing this way over the loader because of the nature of the tool.. when something freezes or doesn't work, is it the theme or the app running files from wrong places ?

secondly, it's very much possible to brick the flash so that you can't recover. the recovery mode is a separate prx in the flash, and with it, it has an RCO associated with it.
if you destroy this file the recovery menu will not work as an incorrect rco will make the menu freeze upon load. I did find it but i forgot what rco it was. I'll post that here once i run into it again.

it's nice to see interest spawn in this area.
i thought im all alone :P