Re:
Bugger, a Tange G Master isn't going to work even if I chuck the locking nut and spacer. I had thought it might fit when I first saw Nick's pictures but it looks like I'll have to have a re-think.
The steerer (174mm) minus the headtube (140mm) is 34mm. I'm not sure if it's an M730 or an M735 that's currently fitted but a G Master will use all available thread before I get to the spacer/locking nut.
Got any suggestions?