Updates:
Got some excellent help via private messages from a couple of men who mount a lot of scopes. Thank you.
Second, re brittle epoxy: Golf club glue. There is an epoxy specially formulated for high impact strength. It retains a bit of elasticity rather than becoming brittle. It is designed to glue golf club heads to shaft, etc. I ordered some. Brampton and GolfWorks seem to be the two main brands of it. Impact of a golf club face on a ball should be somewhat similar to recoil.
