I personally don't think there is such thing as over tightening, at least until the screwhead breaks or if you're using steel rings that are just a touch too small or the scope body a touch too big. I can see scope tubes getting crushed in that case.
I welded some steel bases onto a rifle not too long ago, then welded the steel rings to the bases and put a small tack weld on the ring piece joints once I had the scope in place. I honestly can't say I regretted that choice. It is a cheaper play rifle, and a quick touch with an angle grinder would remove the weld if/when I need to get the scope off, but I haven't see any negative to doing that yet.
I do think I will try the nail polish trick on several other rifles I have laying around here though. Good idea.
