I am of the opinion that if you need any sort of goop, glue, tape or the like between the rings and the scope you'd be better served by figuring out why they don't fit or upgrading to rings that are adequate for the job at hand.
Shear strength is right. Most silicone sealers, various tapes, etc, have less than 100 psi shear strength. With only 2-3 square inches of effective contact you're talking a couple hundred lbs of force required to fail. That's not much. Many adhesives (epoxy-like) can offer a couple thousand psi. That's what the glue's strength is rated for itself, its adhesion to your scope and rings being anywhere near that strong is not assured. So unless you're literally gluing them together with something equivalent to bedding compounds for a near permanent bond (rediculous, unnecessary overkill IMHO), you're likely doing more harm than good as softer substances will be compressed, ooze out and reduce the clamp load of the rings on the scope.
8 properly torqued ring screws offer over 5000 lbs of clamping force. The cf of various types of aluminum on aluminum is typically well over 1 which means well more than 5000 lbs being required to move the scope. Now that's bare, anodizing can reduce the cf but as you can see even when reduced significantly you're still talking several thousand pounds of holding force.
Where I believe many go wrong:
Over lapping such that the rings halves contact each other and don't clamp the scope. This is easy to do with some brands, impossible with others.
Lappping so "well" the rings are literally polished to a very smooth finish. This will lower the cf. You might actually want to rough them up a bit.
Screw torque being incorrect for various reasons. The screws and the holes should be very clean. Many use locktite which after using on the rings a few times can lead to a bunch of buildup that gives false torque readings. I suggest clean screws and holes with a drop of oil on the screws.
Upgrading to rings that use 8-32 screws can be helpful as they'll better handle an increase in torque if you desire. If you're torquing 6-32 screws much more than 20 in-lbs and they aren't grade 8 you're they are likely yielding and losing their clamp load on the scope.
Upgrading to 6 screw rings for sever applications is a much better way to ensure no movement than trying to glue stuff together.
Another tip--while it's impossible to know the exact finish every company uses on their scopes so it's impossible to get exact cf numbers for everything, but typically aluminum will have a higher cf against such coatings than steel. So, especially if you lap your rings you might find aluminum rings hold the scope better than steel.
Hopefully that helps.
