I'll second what was said about the slapping hand. It looks like you are attacking the mat. A lot of people do this, and I'm not sure why exactly. The point of that hand is to distribute momentum, and slapping it barely does. Think like pressure point strikes…hit and stick. The purpose of that is to distribute energy from your body to theirs. Same deal for ukemi's slapping hand - distribute that momentum through your arm to the mat. If you can get your arm hitting the mat well before your body, have it stick, then let your body come down a slight angle from your arm, you will be landing a lot more controlled.
My uke for my nikyu test did that. The testing result was that I looked like a total badass because it appeared I was slamming him. There is totally a fun factor in having an uke that hits so hard it makes you look awesome. That being said, I'm pretty sure the net result is going to be you winding up in a lot of pain later on down the road. I won't say that slamming the mat full force with your slapping hand should never happen, but be aware of it and only do it at times when you want that extra effect, imo.