I have never did it i my own home for for myself, but I did work at a bathtub plant when I was first out of high school. This was the process used to make acrylic tubs. you would heat a sheet of acrylic to a very specific temperature, then lower it down onto a mold, and allow it to settle for a moment, them pull a vacuum for about 30 seconds, then allow it to cool, finally remove the finished tub from the mold, and send it off to have the fiberglass and wood reinforcements sprayed on the backside. one thing I remember was you NEVER did this process in "manual" mode, because the temp needed was very precise, too much and it would sag, and cause wrinkles or low spots, too little and it wouldn't sit down over the mold, or it would tear/crack.
I dunno how realistic it would be to do home vacuforming without having the proper equipment. But I would be interested in seeing if it was possible, thats for sure.