You would want to grease the surfaces before you apply the epoxy. This way it won't stick to the casting or the pylon. It will only fill the void(s) in between the two parts.

I still prefer the shims. It allows for adjustment without having to start all over again. If you do decide to epoxy, make sure the hulls are level both along thier axes and across the hulls. You want the boat to be as "flat" as possible. I think I explained that well enough.

That was a very good point about hitting the castings.