Best IWB rig I've found in that category is the Alessi MOB. It adds just two slim thicknesses of leather to the guns width, the smooth side out doesn't tend to grab shirt material and cause it to bunch up. That, and the single clip allow the gun to shift just a bit as you move, instead of holding rigid in one painful spot.
I wear mine just off the spine. I've worn it driving and out-and-about for as long as 20 hours at a stretch, and it has remained comfortable. The radical rake, meant for MOB, keeps the muzzle off the muscles that usually start to get sore after a few hours. It is also fairly accessible to weak-hand up to about 4:00, for me. No revolver experience with it, but it has worn about the same with a S&W 4516, SIG P220, and a S&W 3913.
