Vacuum Forming

I plan on making a few cowlings for RC model aircraft and need to form them out of plastic.  Mining the web I got some ideas on how to proceed. My experiments are using Poly Styrene obtained from Port Plastics in Chandler AZ . 

Here's a link to the product: http://www.portplastics.com/plastics/commodities/PrimeImpax450PRI.html