Enlightening as always Chuk! Noticed some changes to your formats. Looking good and as they say a photo is worth a thousand words (well at least a few hundred anyway) 
I also have my old Mattel Vac-U-Form still. All the parts molds etc, and even a couple 3 of the original plastic sheets. Made a jig years ago to drill the holes in new replacement sheets.
As to plastics I have used, Styrene seems to take too much heat, thus as I see you have the aluminum heat cover. I found that .010 rigid vinyl works great in the MVUF. It seems to have a lower softening temp and vacs perfectly. Pulls down quite easily and is as rigid and glueable as styrene. I have used rigid vinyl sheet, cut to size in red and transparent blue. Still have quite a stock of the transparent blue sheets. They vac, cut, glue, paint and about anything else that evergreen does.
Check with a plastic supply house in your area. If they don't have any, they can get some and the base color shouldn't be too much of a problem. It is also a lot more economical than buying Evergreen sheet. I like Evergreen, just not for the Mattel.
Here's a pic. One gold chrome, 3 yellow and a molded blue original Mattel sheets of plastic. The dark transparent blue sheets were cut and drilled from some stock .010 rigid vinyl I bought and cut up years ago. I have over 100 sheets of this stuff and it works great. Just wish I could have gotten some clear or solid color stuff. Have used red in the past and it worked just fine too.
Cheers! 
Paul
P.S. The fuselage halves are my WW1 Hannover CL.IIIa that I am building over in the Great War Build. Thinking about starting another thread to cover it as I have been doing a Chuk style documenting of the build. So far my posts are on pages 47, 50, and 51 if you are interested, or PM me.
Keep up the great work Chuck! You keep pushing me to do better and it's FUN!