…took longer than expected, but the Bondo finally cured, and I was able to fill the shell wall voids with foam. It was more than a little surprising that it took so many cans to get it done- 12 in all. The clerks at the local hardware store where I was buying all this spray foam were, not surprisingly, giving me the twenty questions routine. I’ve learned that telling the truth in these situations is not always the best policy. 
It needs to stabilize for a few days before I can start trimming and sanding it down.
Learjet 45 Simulator Cockpit Shell with Foam