I have the Peloton 97 pants as well as Montbell ExLight Down Pants for my lower half insulation. I like leg insulation below 40 because my typical trip is hike a long day, chill for a couple days, hike a long day out. When you’re putzing around camp or just doing a day hike, a lower layer is very nice in sub-40 temps (to me at least).
I normally use the peloton 97 bottoms as sleep pants, as they only weigh like 4.5oz which is less than a 150 merino layer and dirty clothes/skin never touches my quilts. They are good down to around 35-40* static and low 20’s while moving. I wear them with boxers, but otherwise next to skin. The zip off ability is awesome. On cold mornings I’ll start the hike with them on. After I warm up I’ll stop for 20 seconds, drop the pants, zip off the Peloton’s, stuff in mesh pocket, pants up, keep going nice and warm. One thing to note is they are cut rather short (like 28″ inseam for a medium) because they are cut with high top socks/boots in mind. I need high top socks to prevent skin being exposed.
When its around freezing and I’m static, if I’m standing around my legs are generally ok in the Pelotons. But if there is a cold wind or it gets much below freezing, I throw on the ExLight down pants (3oz fill, 7oz total). I have not found their lower limit, but its below 20. Its sooooo nice to have toasty warm legs at camp. In addition to general lower half comfort, I find the pants add 5-10 degrees to the puffy comfort temp. I can get away with my Cumulus Primelite slightly below freezing with the down pants, but consider freezing the Primelite’s lower temp without down pants.
My go-to setup for 25 degree temps while static is – Peloton pants (worn as base layer) 4.5oz, Montbell Exlight Pants (7oz), Regular hiking pants (mostly worn just for pockets and to protect the MB’s. THe pants are kinda baggy so do not impede lofting, weight not counted as they are my primary outerwear). On my top I wear a 120 merino/poly base layer (4.5oz), Macpac Nitro (Alpha 90) 5oz, Plasma 1000 parka 9oz, lightweight hat (1.5oz), and a Peloton97 buff (1oz) if its windy.
I am a night owl and refuse to go to bed for warmth, thus an adequate puffy and down pants make the evenings much more enjoyable in the cold season. That setup makes me the last man standing in my group after the others retreat to bed to find warmth.
My feet are slightly cold at 25*, but I havent found a light/modular solution for them. I am thinking down socks with no bottom that drape over my shoes (trail runners).
That all adds up to 2lb of wearable insulation, but ~12oz of that is my sleep clothes (which I consider mandatory), so I have ~20oz of additional insulation between the ExLight pants, P1K parka, and Nitro. I think that setup could easily get you into the low teens if you add a shell over the P1k and lower if you are cold-hardy. (I used to be, but am now a total SoCal cold-wuss acclimated to 80-90deg who gets cold at 65 with a light breeze. lol)
And although I generally love Kuiu, I do not recommend their (or anyone’s) merino bottoms for leg insulation below 40*, as they are not warm for their weight. Choose either the Peloton97 or ExLight pants or both. (both together are only 2.5oz more than the Merino 200 but are much, much, much warmer).
I got a pair of Farpointe Alpha 90 pants in 2020 but sold them as they didnt fit well (not articulated, no crotch gusset, high waist). He said he was going to make a more articulated pattern last year so recent ones may be better. If I did this route again, I’d have him make a Double layer Alpha 60 as stephen’s articles show 2×60 alpha is warmer than 1×120.) I think this would work great for me as my normal hiking pants are the RailRiders Ecomesh which have zipable vents down both legs. This would work great with the Alpha as I could effectively vent for comfort when moving, though I would choose different pants if it were 20-30 daytime, vs my normal 20-30 nighttime.
Also Goosefeet Gear and Western Mountianeering offer down pants with zips. the MB’s dont have a zip, but it would be nice in the morning when its time to take them off. Probably a 1.5-2.5oz weight penalty tho