I use an eberlestock pack on the sled. The weight of the pack is mostly on the seat anyway and you can keep your gun snow free. I see you said you won’t be haulin butt but you will need to be moving quick enough for your sled not to over heat witch usually means it will be throwing some snow weather you like it or not. Here’s a pic from this years late hunt.
If you have a fan cooled sled speed doesn't matter, most of our sleds are fan cooled that we use hunting.