Well I bolted up the engine and balanced the plane again last night and now it looks like even with a 5 cell battery all the way in the rear, I will still need the equivelent weight of one and a half AA cells on the rear tail float to balance. I cut open the bottom of the fuse and had a look last night and I think I can mount the servos inside and use the current control rod tubes for the outputs. This would protect the servos from water. The battery pack in the rear with the servos should get me really close to balance.