Can you describe what your layering system is like for cold weather sits? Do you wear your saddle over everything or under?
I have some very light jackets and light bib overalls and heavy versions of each. I also have light and heavy base layers.
I usually only walk in with my outer layer (light or heavy depending) and base layers on.
I walk in without my saddle on.
If it is cold, I have in my sea to summit waterproof compression sack a Sierra Design goose down vest and the same but in a jacket. I also have a Charles River windshirt in that sack and if very cold Kuiu super down pro pants.
Once in the tree, I take off my jacket and put on the down vest, then down jacket, then the windshirt, then my jacket back on over it all, and then put a full length armguard on to hold down these layers. These are draped over the saddle and tightened and tucked as best I can to avoid a draft, but I have bibs on so that helps with that. The down pants are full zip off and can be put on like a diaper. They go over the saddle and under my jacket and other upper layers. My bridge loops and bridge emerge from all of this. On my base layer, I stick on 2 to 4 hot hands adhesive body warmers. I have hot hands super warmers in both jacket pockets and keep my bare hands in there.
On my head and neck, I wear a fleece neck gaiter to keep heat from escaping from the neck line an then wear an ear flap hat, the stormy kromer rancher is the best I've found for very cold weather.
On my feet, I wear a liner sock under warrior alpaca toasty toes socks in a tall leather boot with 400 grams of either thinsulate or primaloft. Once settled, I put my boots in arctic shield boot blankets. I have a mesh zipper pouch sewed into the interior of each boot blanket that holds a hot hands super warmer.
When I have to use my hands to setup or tear down, I wear neoprene gloves by glacier gloves, sometimes with an additional liner glove.
With this system, I can not sweat on the way in and hunt down to the single digits without moving for many hours, and I have low body fat and get cold easily.
I mix and match the weight of my base layers and exterior layer and which midlayers I pack in and use based upon the temperature. I sometimes just wear a larger than needed button up camo shirt on the walk in and then put goose down under it.
The key to me is not to sweat on the way in very much.
I try to feel cold when I first start walking and feel like I should put on another layer while walking, but then I don't. I usually carry one more layer than my brain thinks i'll need. Like if i think i can skip the vest, then i should bring it.
A lighter layer that can replace the down pants, is oversized fleece camo pajama bottoms. I'll sometimes wear a base layer and jean weight bib overalls and then once in stand, i'll pull the pajamas over everything. They'll stretch right over your boots and are very quiet and add just a smidge more warmth.
I tend to favor lighter base layers even on cold days. I tend to think that most of my insulation should be in my packed in midlayers. The base layers are for comfort and moisture wicking and the very outer layers are to keep the wind and rain off of me.