A lot of people have already pointed out, bases and receivers do no always match. If the radius on the base is only slightly larger than that of the receiver, the only contact will be in the middle of the base. This will allow it to rock back and forth.
One can test this by mounting a dial gauge on the barrel and placing the indicator point against the objective bell of the scope. By pushing on the scope, you can easily deflect it by 20 thou or more. When you release the pressure the scope should come back to zero. If it does not, there is a problem with the mount. By epoxying the base to the receiver, one can be pretty sure that is not the problem. I would rather not use aluminum bases either.
Re. trigger shoes: One thing a trigger shoe does is, it locates your finger in the same place for each shot. This gives a more consistent weight of pull. Of course, simply shaping the trigger correctly can accomplish the same thing. I always felt that Canjar did a good job of this.
While not many of us torture test our rifles like Limp Stick does, we should all want our rifles to be able to perform that well. Scopes and mounting systems should be tough. A person should be able to use the scope as a carrying handle or let the rifle slide around in the back of the truck. You may not plan on tossing your rifle on the ground but a real hunting rifle should be able to take it. A scope is an aiming device and, if the mount shifts around, it won't do a very good job of aiming at the same place.
By the way, I glass bed my scopes into the ring, rather than lapping. In essence, I am making my own ring insert. It is possible to build some elevation into the mount this way as well. GD
