A few vacuforming questions

I just got a vacuforming table done, and I just have a few questions regarding vacuforming:

i) Could I get a list of plastics that are good for vacuforming? All I can remember is ABS and Stryne. I'd be using this mainly for Boba Fett armour.

ii) Is it safe to vacuform over an existing piece of armour, such as Boba Fett armour by MB or RA? I am afraid that it would damage it.

vaccing over another thermo plastic is risky at best ,the heat most likely warp the original....vaccing off of fiber glass is safer ,but if its fairly thin ,you could crush it under vaccuum
you're better off making plaster positives from inside the pieces you're copying, right after you send that royalty check to the original maker of your armor...he did all the real work ,right?
If you want to see what a vacc table can do to a hollow buck (thats what I was raised to call the item you mold over) just put an empty plastic soda bottle on the table ,place a garbage bag in your plastic frame (loose and saggy,so it can flex) and put it over your table like you normally would (don't heat it tho!) turn on your vacc and see why solid bucks are neccessary ,it will do the same to that arm/leg/chest piece you don't want to ruin.