I claim no credit for the system.
If memory serves I read about in an article many moons ago by Nick Jenkinson in one of the airgun mags. It is permanent but does mean that the scope does not sit on the front edge only of the front scope mount base.
I have not used it as if I have this problem I make a set of adaptors to go between the mounts and the rifle dovetail with a taper machined in but the epoxy putty is a cheaper method.