For what it's worth, I occasionally shoot 357 out of a 640-1, an all steel J-frame. Have some Jordan Troopers from Herretts on it that cover the back strap, too. It's quite comfortable.

A good set of grips/stocks will make a difference, too, in comfort.

To Barb's and Wheelgunners point, 357 from an N-frame is no problem at all for most people.