Mark,

how about going up to a 12mm sheet, in a very soft braid, so it flattens over your hand instead of cutting into it? Having a large diameter sheet makes it easier to hold the sheet inside your hand instead of wrapping the sheet around the hand.
If your hands hurts after sailing, my opinion would be that you use too much force. That is why I mention things like friction, more purchase etc.

Here is a pic of the best way I have found to hold the sheet if you can not just hold the sheet in your hand. It was posted on the open forum some time ago by John Williams I think.



PS: Mark, in another thread we concluded that oversheeting was catastrophic in a race. Undersheeting was not as bad, but still not fast enough to keep up with those who sheeted optimum. I would want to check my max-sheet point compared to others