I’ve got a couple of pairs of 661s- a set of Bomber Pros and a set of Evos (d30). The Pros are basically dh kit- quite bulky. Very good coverage though.
The Evos are xc-able, though a little sweatier than standard lycra shorts they’re not bad at all… But the protection’s not quite as good, the pads work but they’re not as complete, and weirdly no pads sit quite on the end of my hips which is probably a bit of a miss.
I’ve crashed pretty hard in both without any issues (I have osteoperosis and a load of metalwork in my hip so that’s better than it sounds!). But I don’t wear them that often, the extra sweat level is just enough to be annoying.