There's not enough structure near the tail to move the servo's to, I would if the structure would support it, I would have to rebuild the tail section to have a solid balsa wood structure. The fuse in not solid balsa wood.
I moved the engine back once, the fuel pump is hitting the motor mount, I could gain about 1/4" if I were to shave the motor mount to allow the fuel pump to fit closer to the firewall.

I see where you guys are going with finding all the weight in the nose, the cowling, prop and spinner weigh 10 5/8 oz. I have pretty beefy screws and nuts to secure the engine to the mount. The prop is a K-series Master Airscrew 15 x 8, can use 15 x 8 to 16 x 6 props with this engine. How do you go about getting a lighter cowling?

I think relocating the battery towards the tail shouldn't be that difficult.

The first pic is the fuel pump/motor mount issue.