A gunsmith I know who has to do a lot of work with rifles chambered for the .338 Lapua recommends the Pachmayer XLT. I've used one, and am happy. His sample size was a lot bigger.
I've used pads made of sorbothane, like Decelerator. As somebody said, it takes a set. In my case, with a 17-pound rifle, a bulge. Ways around that -- store it muzzle down, or have a removable pad. Did I mention it was a big, ugly bulge?