Luv2safari, what i was refereing to was the EAW twist on mount, being a good bit cheaper than any claw mount, and are just as good, as far as returning to zero! The re-regulation may not be needed at all.

Mickey, Warne makes a gun smith base that is about 9" long with three base sections on it with screw holes for each, so the bases can be cut in to three different length bases, and fitted how ever you need. The bottom is flat, so it can be fitted flush with the top of the rib. If your rifle has a quarter rib, they are usually left fairly thick so different sights can be installed.

Luv2safari, The trouble with drillings, or older double rifles with a single raised rib is, the top rib is uaually the same as a shotgun, and is hollow, and depends on a very thin edge on each side for soldering. A scope will sometimes remove the rib under recoil. In that case solid blocks have to be fitted, and soldered to the barrel surface to hold up. That is very expensive, and takes someone who knows what he is doing, and usually requires refinishing the barrel set.