Just finished the same type of modifications to the Super Stearman, I removed the balsa block ahead of the wing saddle and behind the firewall. These are only lightly glued in from the factory so they are easy to remove. That allows room for a 1/4 ply doubler to be epoxied behind the firewall. I beveled the sides so it would fit tight between the tri stock on the back side of the firewall. By opening up the bottom of the fuse, I could also add some additional tri stock to the formers to strengthen them as well. Finally I found that the formers need to be relieved to ease the access to the Syssa stand off bolts. Likewise I removed the stock fuel tank mount but added a block and blind nut to the back end so the tank can be removed. I learned these tricks after having the front end of the fuselage apart to make repairs, and when I put the Syssa on the fuselage the first time.