This is an interesting question, and I have no unqualified advice to give you.

Your analysis of the requirement for a tight fit is absolutely correct, for
obvious reasons. I work in a kinda crappy, used bike, coop shop on
Saturdays, so as you might imagine, we do this operation a lot. The bikes
that it gets done on are also all over the map.

Are the races you are seating in the head tube not tapered a little bit
where they go into the head tube? I've seen headset cups pressed in that
did not appear to fit, but I've also seen crown races split when pounded
home on the fork, and I understand your reluctance to trash a Chorus
headset. Usually greasing the cup males and the head tube ends
seems to be enough to allow the press to work its magic.

Anyone else who has actually measured the headset in question?