Thanks for the suggestions, I'll give the 2-sided sticky tape idea a try. Doesn't anybody else have this problem?
I dont, and I have the same shoe and cleats. Never did any sandpapering to either sole or cleat, nor have I ever used a medium such as doublestick tape or somesuch between them. When I install new cleats, I simply bear down on the screws with significant torque, but not to the point of completely overdoing it.
I always have the Swiss Army type tool thing with me on a ride just after cleat installation because they used to shift a little sometimes on the first dismount. I remember this was more often on a new sole, but my current SIDIs are nearing where I might replace them and maybe now have the equivalent of a little roughing of the surface built in. In any event, after this first ride, they always set right in and stayed there very solid. Never had a problem afterwards.
Maybe try a little roughing up of the cleat surface itself wear it contacts the sole. You could use a very fine sandpaper and a really light touch. I'm honestly not sure you'd need anything more than that. If you have a home trainer, which is where I now test them after install, just get in and out a few times and then double check the positioning. Once they shift once and you fix them and tighten them back down they never again move for me.