I managed to obtain an aluminum disc fork intended for Chinese domestic Dahon frames, but the steerer tube is about 12 mm too short for my Novara Flyby (= Dahon Mu) frame. I did some digging and found that there are at least two Dahon headtube lengths: 87 mm and 99 mm. My aluminum frame, as well as a few Terns I looked at, are 99 mm.

Does anyone know which frames have 87 mm headtubes? From what I found, that might include the steel Dahon Speed frames. Thanks.

ooops ....
would be interesting to find out where you got that fork, as I am looking, begging etc etc to get some myself. You can pm me with the aanswer :-)
You are right Terns and Dahon bikes like the jetstream have a longer headtube...pretty sure the mu models as well..... most others have a shorter ones

I have some suspension forks coming my way and those have a longer steerer to fit both :-)
Best Thor