I am in the process of building my firewall. It was suggested to me that I should reinforce the firewall box with a horizontal steel tube between the two upper and lower engine mount brackets (Corvair mount). The basis for the statement is that the lower horizontal wooden strut is cut at the ends to allow passage of the brackets and the upper horizontal strut is several inches below the brackets. The plane I saw has the motor mount bolts screwing into steel rods that run between the two sides and are safety wired. Any engineer input out there would be appreciated.
Jeffrey Kornblum