Nick is basically right re: wrapping a piece of running rigging around your hand being a bad thing, but the mainsheet on a Hobie Cat is not going to drag your hand through the blocks. Especially considering that in heavy air, you're about 8 feet way from them on the trapeze.

I use exactly the technique that Jim describes for controlling the sheet in heavy air. I don't have the strength in my hand to hold it otherwise. Witness me taking a wrap around my hand: