Just curious why you all think you need insulation on a Drum Smoker?
I've cooked on mine when it was 20*F outside and other than using a bit more fuel than usual (15 lbs rather than 12) it performed like a champ.
They use less fuel than an 18" WSM, and you can't even compare them to a 22" bullet for fuel use.
Reflectix has a 180* heat range. But if you coat it with aluminized duct tape it'll have a slightly higher range, but its still plastic bubble wrap! A welders blanket would be my choice if I ever felt the need for it.
Why waste a good overpack drum when you can make a Magnum drum using 26" Weber cook grates?
Yeah the Winters in Alaska or South Dakota are rough, but you'll probably have more issues with wind than the cold weather. Seriously-I'd consider making a wind break out of plywood and hinges that you could fold around the drum and still work with it.
Oh yeah! The reason I'm finding it harder to find reconditioned overpack drums in Seattle is because they get shipped back to the oil fields in Alaska!