The strongest setup is to set the firewall back about a 1/4 in so the sides of the fuse are forward of the firewall, then put triangular stock in the front and back corners of the firewall. When you stop and think of it, when you pry back on the landing gear, the top of the firewall is being pushed forward. The triangle pieces on the front will strengthen this a lot. For the triangular pieces, with the grain of the wood going vertically in the corners the triangular pieces split fairly easily. Buy a piece of 1/2 in thick balsa and put the end of it through the bandsaw cut on a 45 degree angle. Make a bunch of pieces. Glue these trianglular pieces in the corners and you see where the grain goes across from the sides to the firewall. Much, Much stronger joint. Trix learned from scratch building since the 60s