Mark, I feel your pain, litterally! I've had that kind of pain several days after a windy regatta too. I just bought a new mainsheet which is that new soft Mafioli line, and there is about 10 feet of 4mm dyneema spliced in at the tail where it runs through the blocks.

What I found was it is much easier to trim, requires less "pull" due to the 4mm Dyneema running through the blocks I guess, but it is also less "hard" as my old cored sheet was and when wrapping the new one around my hand it doesn't hurt as much.

You may notice I didn't say doesn't hurt -at all- just not as much.

Oh, I also wear the cheap rubber coated cotton gloves you can buy in a hardware store because I find they grip the sheets much better than wet leather gloves, and at only $3.95 per, I can buy several and toss them when they wear out. That extra rubber gripping power means I don't have to squeeze the sheet so tight to trim it which helps alot, and it also helps me when dealing with skinny lines like the spin halyard/snuff line.