That more folks aren't asking for this. Back in the day, EVERYONE who was a rigid SS rider rode the Weirwolf 2.55 tires for their balloony cush - but on the front only, as they were a pretty crap rear tire.
I figured people would be doing the same with the Knards and I'd be building a bunch of rigid forks specifically to fit the big rubber, but I think Minh's is the only one I've built. 100mm axle spacing and 100mm of clearance for the tire, so the blades actually angle outward.
Pulling the chariot might not seem like a job for a 3" front tire... but maybe the commute to preschool is more gnar than we realize.