Vaccu-forming "acrylic" material can be a PITA ! A few years ago, when working for a local Scenic
House. I was asked to create a "Space Helmet" for a cucumber....... Yes a cucumber. It was for the touring company that does Veggie Tales. I was daunted. This thing had to be 20" tall, about 18"in diameter at the bottom and then tapering to a rounded
point. If you've ever seen and of the veggie tales videos with them in space you'll know what I was emulating.
Anyway, I did some research and eventually found a Teflon based plastic called
PTFE. You've probably seen it used as a slider on something, it's usually white and slippery. They make a sheet version of it that is
clear and one demonstration of it's properties that I observed was a mask with a long pointy nose that was about 24" long and only about 1/2" in diameter. For those of you familiar with Vaccu-forming you know that this shape would be practically impossible to pull from a standard piece of plastic.
Ok long story short, too late, you could easily pull a shape like that from
ptfe, you can try acrylic, but everything I've every pulled from Acrylic, if it's more of a curve than say a skylight shape, tended to fail miserably.