I managed to fit some 2.125 duro whitewalls on my last fendered ride and the fenders on that bike seem quite a bit narrower vs the peaked fenders on the AMF. I think I had maybe 1/4'' clearance on either side of my front and rear fender struts at the tire, I did have to bend out the struts a wee bit though. not by much, but I made it work.
I can test fit a wheel sometime this week with the Duros on it, since I'm basically working with the same bike lol.