There's nothing wrong with slapping hard - personaly, Iove it. However, you also have to learn to fall without slapping at all, and something in-between the two. Learn in the dojo, try it on the grass, try it on a hard floor and you will naturally find yourself moving from a hard slap to none at all. The problem is if you only train it one way. In the dojo I whack the mat quite hard, purposefully, and then when I do
irimi-nage I kinda hit them - in my mind - with that same mat-slapping power (without really hitting them of course, but I could if I wanted to). I love it and have been doing it that way for years. I have been criticised, but basically, I don't listen as I have my own reasons. What I want is to be able to fall with a hard slap, a soft slap, and none at all. I also like to fall and hit the mat with
uraken, hard, so every time I fall I get a bit of extra conditioning. Try it, you might like it