Ray would be a better person to answer this but if you are going to try true S/H the important thing seems to be to keep water in the bottom well at all times. I'm not sure you can really overwater them in true S/H.
I was just asking about Plain LECA, and not an S/H set-up.
But on another note, I always figured S/H would kill something like most cats, being that they seem to like to dry a bit between waterings