Hey Mulling & welcome to the forum. The donut is vacuum formable I believe. However, the durability of the item is a function of its end-use. Since vacuum forming is a stretching process there will obviously be some thinning of the material in the donut hole area. I don't stop by here very often so you may try http://www.tk560.com/phpBB2/viewforu...bdd1fa6f2ef703. The vac forming conversation is slightly more robust there.
Good Luck, DougN