The other problem with mounting things to stone walls is that the face
of most stone walls is irregular, and all of the anchor points of
whatever you are mounting must be right up against the stone or the
anchors will just pull out as the screws are tightened. We run into that
mounting the electrical disconnect boxes for a/c units. I keep a
variety of nuts, washers etc, to use as spacers, as well longer screws
to use with stone. Larry