Buzz's parts were really easy. They don't have much volume or detail, so I could knock out the full set of four in a single shot.
The rule of thumb for heating the plastic is that the volume of the sag should match the volume of the plugs. In this case, 1/4" would be plenty. I goofed off too long while the first sheet was in and it sagged enough to vac form the head off of my 351C-4V.
Once the second sheet of PET had sagged its 1/4", the shop vac was turned on. The frame was pulled from the oven, aligned over the weatherstripping seal on the table top, and dropped into place. The plastic is very rubbery and it pulls down in the blink of an eye, but it cools just as fast.
Extremely important tips:
WAX THE PLUGS! If you don't the plastic will stick to the plug and it will be destroyed in the ensuing removal process. I get very angry when this happens.
Remove the filter from your shop vac. Its suck factor will improve dramatically.
Replace the filter when you are done. Guess what happens if you don't. No, I haven't done that one.