Well, I can't speak to drilling holes in them, but something I have done on a couple of mine was to glue a clear plate or even a block of wood to the bottom and then cover it with mulch up to the figure. Keeps them in place and you don't see the block. I usually use either liquid nails or GE Silicone II and so far it's worked fine.

You know I have wondered about this too. I've thought of putting some mortar mix inside then shaking with the right amount of water. But it seems like you would need to make another hole for air/drying once you plugged the one in the bottom and stood it up so the weight of the mortar would be at the bottom. I'd like to know if you figure anything out. I like Marlene's idea also.
Kathy

I sink rebar into the ground and set my things on top of it so it cannot blow over or be knocked over by the critters. I wonder about that Hypertufa...