Thanks OldBob! I'll be sure to remember that. It makes sense that nothing could be a better base for silicone than something non-porous like epoxy.
I've decided to go with 8611 Titanium servos. I think on a delta, the elevons punish a servo more than your roll control servos will see on a Q-40. If the 8611s fail, there won't be as much second guessing.