I've seen pic's of the Knard fitting in Fox forks. I guess I've never put a Fox fork up against a Niner fork but having seen a few Niner forks, it seems like they may have more clearance then a Fox fork.
I tried one mounted on a P35 and it does fit in a carbon niner fork. It is a tight fit. It had about 3/16 to 1/4 of clearance on each side. I was only able to ride it around the block but I tried and could not get it to rub the fork, but I only weigh 155.
Interesting! So it does fit but you might end up with some new shaping to the inside of the fork....I've managed to rub the chain stays on my superfly with a maxxis ignitor so not sure I'd want to do the same to the niner fork. Very tempting and would save me buying a couple rigid forks. Wonder if the maxle version of the niner would help prevent the tyre kissing the fork?
EDIT: fjtort do you have any pics from the front? Be interesting to see if mounting on a rabbit hole helps with clearance