The Thin CA and the CF re-inforcements do not add appreciable or noticible weight so you're OK there.

Don't go overboard though. Remember that ply is stronger than balsa structures. Sheeting is not going to add any appreciable structural strength to what you have.
The truss is a better idea IMHO and easier to do. If you want to go further you could lay thin CF rods along the existing wood ones.

You should see my Addiction-X.... there seems to be NO supporting structures in it and looks like it will fall apart if you breath on it, yet the plane pulls "G"'s like it is no ones business, thanks to the CF bonded to the wood.


Try to stay with the 20cc and resort to moving things around instead of going to a larger engine.

That will help keep the wing loading low, which will be crucial.

While I don't favor this myself, I've seen a lot of guys strap batteries directly to an engine beam mount to help get the C.G. right.