...I picked up a used fatbike and am having a fricking blast on it, a real lark. It has pretty narrow fatbike rims, 60, 55, 50mm? the narrowest for 4in tires anyway, so maybe could take 3inchers or something narrower. But it is 26" so not really sure that there are any options for plus size 26ers anymore, will have to figure out what can fit onto the rims, and we've got the whole winter to get through anyway so 4 inchers it is for a while.
Am just starting to get my head around how low pressures I can run, 5.5 psi has been great at times, even with undersized tubes (3" downhill tubes)
cheers
Fat bikes are fun. I'm still pretty pleased with mine. In retrospect, I think I would prefer the option for narrower tires as most of my riding doesn't take full advantage of the float 4.6 offers. But... still a fun jeep jeep bike
Funny about pressures. I don't have a very specific gauge (just the one o my Park floor pump) and usually run mine quite high. I find I get enough cushion and desire the lower rolling resistance to cover longer distances.