My tombstones kept getting blown around my neighborhood whenever it was windy. Since some of them were a bit too skinny I came up with a way to windproof the gravestones by cutting out a notch in the back and then "glueing" PVC in place using Great Stuff spray foam. It worked fantastic for reenforcing everything. If you're using thicker foam you can probably just drill a hole and insert the PVC into that.

Some I only use one stake, but you risk it rotating on that one point. Using two is way better, but I didn't have a lot of rebar and one works fine on my smaller headstones.