Well first of all, you could build in some light ply on one side of the fuse for the switch to mount to. You will also do well to use a little glass or epoxy to the wing joint. As you have noticed, the fuse sides are pretty light. Reinforcement along the wing saddle is advisable, as well as the wings where they contact the saddle. This plane flies great with a 40 size engine, but you might consider something a little bigger. As for the lower fin on the rear, mine came to me already mounted. My left wing half was a bit warped though. I never was able to get the warp completely out but it is hardly noticeable in flight. A little trim adjustment to compensate was all that was needed. Hope you enjoy yours as much as I have mine. As mentioned by BBJohn, I also soloed on this plane. Easy flyer.