Ok, so following rsavage suggestion and going thru the many steps as explained in the FAQ, I've been able to create a Persistent Live USB Ubuntu 12.04 thing.

TBH it's probably at least as much luck as it is work (and some reminiscence from my good ole days working in a Unix environment), esp. the section around mkofboot, I've tried to get the most out of reading 20 times the 6-line explanation ^^, gave it a shot ą la "oh what the heck let's just try this !", and voilą, now booting directly from USB flash drive, no need to get thru O/F or anything. Nice !

Next step : RTFM about what "persistence" consists of here, iow what settings can I save - or not save, how it works, etc... and then try it out. Once I have this mastered (lol), I can move on to looking into installing missing drivers, missing plugins, missing applications, missing... ok, enough already !

Too bad this thread and the PPC forum in general doesn't generate more activity, more responsiveness, oh well... (and thanxx a great deal to those who do participate here)