You might try cutting some lightening holes in the servo mount plates. 1/16" birch ply was a bit of an overkill. The Tiger has a lot of wing surface so I don't think you've hurt it too much. If the servo plates span the full width of the rib bay, you might try (carefully) to drill out a couple of half inch holes to lighten it up.

Hey least you'll know that you've got a very strong set of gear!!!

Cheers,