I need to make about a 2 inch motor mount extension to mount a Brison 2.4 with Slimline inverted pitts style muffler. What my concern is attaching the extension to the firewall. I can make a box from plywood but am leery of just epoxying and or bolting the box to the firewall and then fastening the engine to the front of the box. Will this be strong enough to assemble the ply box with epoxy and triangle stock in the corners? or should I do something else that will ensure that everything will stay together. I have thought about using long engine mounting bolts through the engine, through the box and into T-nuts behind the firewall. Any suggestions for a better design?