I use my Hennessy Hammock with the 4-season system in all kinds of weather but haven't been able to try it out in very cold weather yet. One thing I did add was an "underblanket" from Wiggy's, It's not listed on their website but they do make them on a per order basis.

If I used a cart or sled in winter with adequate snow, I'd seriously consider getting a Grand Shelters ICEBOX. Come to think of it, I'll have to start researching carts that can convert to sleds for BOB/INCH purposes. (No affiliation with Hennessy, Wiggy's, Grand Shelters or any cart/sled manufacturer or supplier.)

LINK: Grand Shelters ICEBOX

Quote:

* With outside temps of -15 F and two candles burning the temps will
be 48 F at the ceiling 38 F at the floor.

* With no heat source and all occupants in sleeping bags the temps 38 F
at the ceiling and 34 F at the floor.

* No need to sleep with the water bottle.