Don't worry too much Adam
I'm going to leave it with the 35mm for a while to see how I get on with it. I've also got a 70mm on my Hardrock that I can swap over. TBH I'd like to try the 35mm on the Hardrock as I think it's a bit long in the top tube for me and I doubt it would suffer from having the steering sharpened up a bit
Carbon 456... could be very cool
Bob... the seat post is 370mm... don't know how much is out of the frame but most of it I think.
On One say 150mm fork as the max size, mines 140mm so I supose it's close to that and the frame will be at it's slackest geo. Other than that I'm not going to pretend I know what I'm talking about