Any question answered...

My Feather is 56.5 ST / 55.5 TT, trad geometry, oversize 853 Pro Team, and with forks and headset it's about bang on 2.5kg, so about 2.4kg F&F. The forks are 631, i.e. not super light, so I reckon the frame alone would be about 1.85kg or less. And it's built very solidly. I think you could easily make a compact frame in your size to about 1.7kg.

Great, very helpful, the approx weight should be 1.8kg with S&S coupling and a 550g road fork (Kinesis DC-07) with clearance for 32c, so 2.35kg.

That'll give me something to start with.