On my new frame, the head tube is 231 mm and the head tube is 169 mm. This seems like a way too long head tube. Most threaded headsets are about 40 mm stack height, and allowing 5 mm or so for a cable hanger, the difference should not be more than about 45 mm. But in this case the available difference is 62 mm - I'd need to add up to 2 cm of spacer with a threaded headset!
Is it an absolute that I have the wrong fork, or is there any frame designer's rationale that I'm missing here? The builder recommends Stronglight A9 headsets, but there's no way an A9 will fit here without the 2 cm of added spacer. Could there be a purpose for this design that I am missing?
Edits: I should add that while the frame and fork are supposed to be the product of a known modern constructeur, I bought them from his original custom bike customer. It is possible that the fork was switched by the original owner.