NavyE6FE - you and I have exchanged post in the past. I remember those early post about the firewall coming lose. This was a real problem with the early production runs, especially with gas engines. I found the balsa on mine had gaps you could see a light through right out of the box. I added tristock inside the fuse to the firewall and inside and outside of the mounting box as well. I then pinned the firewall and then added fiberglass cloth with finish epoxy for resin. You may recall that I lost Pitts-1 in a horrific crash which also cost me the Fuji-50. The firewall held though. Maybe the engine might have survived had I not made the firewall so strong, but I didn't want the engine coming lose from vibration.

I did the same on Pitts-II and all is holding tight and snug.

Pictures below show the firewall with the added tristock I did on both Pitts-1 and Pitts-II. Pitts-I went in, but the firewall held. Replaced the engine with a DA-50 on Pitts-II.