Vacu-form styrene sheets?

Skip the holes. You don't need them. I've cut my own sheets for YEARS and only drilled holes once. Just give the clamp an extra push or two as the plastic softens and the teeth will dig in just fine. Unless you are molding something really tall or don't let the pastic get soft enough, it won't pull out of the clamp.

You can also improve your results by modifying the molding platform.

Drill more holes in the platform. Not bigger, just more.

Build a gasket out of silicone or clay that fills the gap between the edge of the platform and the raised metal lip of the vacuum "well". The gasket should be about 3/16 wide and about 1/16 high. If you are lucky, you may be able to find a weather stripping product with an adhesive back at the hardware store that you can rip down to size. You can also carefilly sculpt a gasket with tube silicone. The easy, but messy, method is simply to lay a 1/8 diameter clay worm around the edge of the platform. The gasket will both seal to the plastic and plug that big leak at the edge of the platform. You'll be amazed at how good a vaccum that hand pump will pull.

Greg Reynolds, IPMS

There are at least couple of sellers on eBay selling pre-drilled sheets.

Just search eBay for "mattel vac u form" (no quotes) and check out the results.

Peteski