I use the Lv 7 pants in a LWCG .5 hang on. Kind of difficult and bulky to put on in a little stand like that but it’s doable. They do lose loft fast if you pack them tight in a bag repeatedly. Still usable and great ROI for what they are. My biggest gripe is that they are noisy, so you have to be conscious of your arms/hands/bow coming in contact with them if you’re a sitter, or your thighs if you’re a stander. I wouldn’t put anything over them, you’ll compress the loft, and in my experience putting anything over a puffy layer just seems to make it louder to my ear, since the entire exterior fabric is now scratching on the puffy over a larger surface area.
It’s not a deal breaker, just a quirk to work around. If you’re moving your legs enough to make a lot of noise you’ll probably get busted visually anyway.
One option that’s great by itself or for layering is the M65 field pant liners. It’s a quilted batting so they don’t compress the same as a puffy if you layer over them. Their design intent is to be layered. The nylon is about the quietest smooth face synthetic material I’ve ever seen. I wish it was used more in other products.
I’ve found if you buy 2 pair of the M65 liners, sized long, you can double them up over your legs as a stand alone layer and I’ve found them to be just as warm as the lv 7 pants since they trap air between them. Even better if you get them in sequentially larger sizes (ie a small-long worn under a medium-long). Buttons down the side are easier to get on but can be drafty. No buttons is warmer. Best part is, virtually no noise and easy to slide on over boots/shoes. Also, the “fly” area of the liners is open so if you use a rock climbing harness as your safety system, the belay loop is accessible.
Both options are warmer if you stand since the loft in the thighs, knees, and butt won’t be compressed.