Mike,

I am a little confused about what you said about air blowing your canopy out.

Looking at my model I have cut-out the section inside the engine bay which will have the exhaust pipe going through it. I lined this area between the engine bay and the first undercarriage former with light 1/16th balsa. Then you have the pipe floor on the otherside of the second former provided. There shouldnt be any access points between the engine bay and the inside of the fuse.

As for the CG with a DZ up front does the model balance on the tube if you install elevator servos in the tailplane?

Cheers

Peter