When I was caned by the Deputy Head across the bottom I was positioned over the back of an old armchair. This gave her the space to deliver a full force swish of the cane which she duly administered. When caned across the hand accuracy seemed to be the main concern of the caner.
I have had the cane on both hands and bottom. Without a doubt it was much worse on the bottom. It seems obvious to me that, as the buttocks provide a larger target area, the bruises, and therefore the pain, will be worse, unless the force used was much less.