Hmmmmm..
Well, I would mention here that I think this is a lot of "ado" over something not worth worrying about.
The aluminum pads are mounted on Maple, in most cases, and that still provides some elastic deformation (The compressive strength of maple is low enough to permit some deformation) when the engine is bolted in place. "Viola", not much different than bolting the engine directly to the maple mounts. There is also a small amount of torsional "give" in the fuselage mounts. Add all this together and it simply overcomes the very small amount of draft in the Fox mounts.
If one must...it's a simple matter to slightly bevel the maple mounts {with a file) prior to putting the aluminum plates in place, but entirely unnecessary in my opinion.
Between the natural flexibility of the engine mounts and the case, and the maple mounts, any distortion in the engine case will be completely negligible.
Randy (sensible engineering) Cuberly