Just my opinion:
If I were to alter anything, it would be to replace the solid stabs with built up ones. I would leave the original ones intact, as this plane is capable of really horsing or stressing those components. Without changing the type of wood to something really hard to maintain rigidity, I think control would start to get a little squirrelly. I know that once I get my first couple of flights in spring to loosen me back up, this airframe takes a beating. I think the thing to worry about most would be getting the stabilizers to twist once you start some of the higher energy maneuvers. Possibly adding support wires to the front and rear edges of both stabilizers could help, but how much drag will all the extra hardware add?