bigfish,
First, I would get some video of yourself, you may be able to fix after seeing what is going on.
May not just be your hand turning, but your elbow/arm also. Your elbow may be coming out away from your body, causing you to lose some leverage and have to muscle your swing more. Think about leading with the inside of your elbow, the inside of your elbow coming up through your target. This should help you to keep your forearm and wrist/hand behind the ball instead of to the side.
Your hand position is why you are thumping the holes. Pretty close to being a full roller. This problem can be fixed, but it is going to feel funny at first, you are changing your muscle memory. Your scores may suffer some at first, but I would be willing to bet that your swing gets looser and you become more accurate in the long run.
Hope this helps ya...
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