For me my 666 UHR are slightly short in the rear rise, as they have less of a natural slope compared to my 633/634 XHS.
I was wearing a pair of 634S-B’s size 40, and they got a little tight in the waist so I purchased a 634 XHS size 42. I figured going up a few ounces justified a size up, to make the break in easier. Those fit great in the waist, everywhere else was way too baggy.
After asking on here the consensus was made that I either need a 634 size 40 with a larger waist measurement, or a slimmer cut size 42.
Purchased a pair of 666 UHR size 42 and they are basically “painted on”. The rear rise also doesn’t do it for me, as stated above. They are always sliding down, and they are by no means loose.
Currently i’m wearing a 633 XHS size 40 and they are great. They have a slightly larger waist measurement, without all that extra bagginess the 634 size 42 had.