Moonlanders and Clownshoe rims are here!
The Moonlander is the big brother of the Surly Pugsley. The difference is in the tire clearance and and the offset.
The Pugsley has room for a 82mm rim with 3.8 tires using 17.5mm offset with no chain clearance issues. The Moonlander has room to run full gears and 100mm rims with a 4.5 Big Fat Larry with 28mm of offset.
The name of the Fat Bike game is float. The more surface area your tires have on the ground the more float you get to prevent wheel washout. We tend to only run 3-6 lbs in the snow to maximize surface area. On the Pugsley that Ruda rode in the Alaska Ultrasport last year had 100mm rims with 3.8 Larry tires. The only way he was able to pull this off was to use a 9spd cassette with the 13 and 17 tooth cogs removed and cassette spacers in back of the 36t cog to get the chain not to rub on the tire with a 22-36 tooth chainring configuration.
Call our shop, Ruda knows these things inside and out.