Bases such as the talley have a lug built in and they don't have weak little rimfire style clamps, rather they have screws which have a very large shear modulus 90° to the screws that's why they work on every other gun but yours. You haven't fixed this already?!i honestly think drilling and tapping tiny little screws to hold bases instead of using the integral bases would not be nearly as strong.
There should be a recoil lug for the front bridge , or have the base utilize the front of the action opening similar to what EAW has done with their cz rings. Rigby used the double square bridge when they used the CZ actions, and do again with the Mauser actions. Their rings are quite expensive and I haven't been able to look at a set to see what they do . Their 450 Rigby is only a single square bridge so it cannot utilize a scope
I would imagine you could order a double square bridge and have them build it.
Does anyone on here run those beauty Rigbys and have any input how their ring system works?