I have a bike with a short headtube (Affinity Lopro) and my stem (150mm tall, Nitto Pearl 9) going to the absolute bottom of the headtube is still too far out, like 20mm too far.

I imagined milling the fork but soon learned it was a bad idea because it could compromise the integrity of the fork. Then some local riders suggested that I mill the bottom of the stem but I don't know if it is a good idea.

Is milling the bottom of the stem something that is usually done? Will it compromise the integrity of the stem (removing 20mm from 150mm)? Any other advice (besides getting another stem)?