It's true a daruma eats up clearance. I just mention it because it is an option. I've got one on my PX10 and the clearance is pretty tight, though it does work. Practically speaking I guesstimate it would limit you to ~28c tires, 32 if you push it. I think I could pick up another 2-3mm by grinding the end and using a flatter nut and loctite instead of a nylock.

A threaded boss under the fork crown is really the best way, but of course it will screw up your paint. Another way would be to countersink your fork crown as if for recessed nut brakes, and make or acquire an L bracket that clears your headset. That would give you plenty of room to space out the front.