no vacuum form box yet, but after the amount of work to get the roof acceptable smooth after I formed it I'll probable be making one.
I made the balsa wood buck for and shaped it until I was happy with it. Than I removed approx. 0.040" of material off the top so that when I heated the 0.040" styrene sheet it would have the same shape as the original buck. I removed the balsa from the model and made a larger than I needed piece of styrene and heated it with a heat gun and draped it over the buck form and after it cooled I trimmed it until it mated with the original body.