The SD structure is light being made of lite ply but it is very strong. In areas where I can lighten the structure even more without compromising strength I am doing so.

As an example, I used triangle stock and epoxy behind the front plate (firewall) on the engine box. I also used #6 x 1" flat head wood screws around the sides of the firewall. These were put in using Titebond II. I cut a hole in the firewall behind the engine and on 2 places in F1 former. I glued in 1/16" balsa into these 2 holes because I didn't want engine heat entering the cabin.

Former F2B is laminated between 2 stiffeners F2C and F2D. I removed some wood from F2B.