At my judo tournament this weekend I heard at least one sensei telling his students not to slap the mat. This causes the judges attention and could be cause for an ippon, game over. Perhaps you do a different art where this wouldn't happen?
Beyond that whenever I hit the ground hard and theres no mat or I go off, my hand feels like a tuning fork. Hurts for hours.
Tough weekend, almost got in a nice choke from the ground, and I had a nice hold down going but lost it. I was the lightest one there, and the oldest by a good ten years. Maybe I'll do better in the Bay State Games. My 7 year old took 3rd, so that was good.
Also met some guys from the Olympic Team from Ukbekistan or some such country. They were excellent, after doing fit-ins with that level your eyes are open.