Furry's fat and long bikes

OK...quick question.

In my mind it's perfectly possible to run a non offset 135mm rear on a fatbike with a 1OOmm BB, so long as it's only ever going to use either SS or internal geared rear hubs and single ring chainset right?

The only reason a Pugsley is offset is for chain clearance with triple chainsets and full cassettes right?

Might be doable. Like you say you just need to clear the tyre. Chainline would likely be better with a 170mm rear I guess.

Math time.

Standard MTB chainline = 47.5, with 68mm BB
So Fattbike chainline with 100mm BB = 32/2 + 47.5 = 63.5mm
width of 3.8"(4") fat tyre on 80mm rim = 100mm (ish)
width of chain = 6mm (?)
Radius at max tyre width 372mm

You have 44.5mm clearance at the sprocket.
You have 60.5mm clearance at the chainring.
You need at least 50mm tyre clearance 372mm from the rear axle.
Your chainstays are Xmm in length.

Probably easiest to draw it out on some graph paper. But my guess is it would work. (That example uses the middle position of a triple chainset). But the chainline looks nasty.