Icebreaker frame to fit with 2XL at 20psi on 80mm rims. The shoulder knob width is 124mm. The clearance between CS/SS is about 5mm.
The problem is that the rear triangle does not have enough radius, so the center knob rubs the seat tube. But problem solved by itself at pressure ~10psi or less. To cut the knobs is maybe also an option
So, considering 2XL to be more like winter tire, it can be said that frame could be compatible with 5,05" tires on 80mm rims.
Icebreaker fatbike carbon fork with 2XL at 20 psi with tube on 100mm rim.