QWERTY, love the detailing on your bike. Reckon that’s the most elegant and simple rear brake mount I’ve seen! Also you may or may not be surprised, having spent ages drawing and re-drawing my geometry, wheel size and a bit on both the seat and top tunes aside, the geometry is going to be remarkably similar!
FWIW – 921 painted with some stainless detailing like the driveside chainstay, Logo etc would look good.
The point of stainless for me is that I wouldn’t have to paint it… Lazy man’s option! Suitable 29er profiled chainstays seem few and far between in stainless though, which might bring me back to a mix of 853/631 and Columbus.
I’d go for adjustable / sliding dropouts with the brake mound attached. Gives you far more options for chainstay length and the opportunity to go boost or play about with geometry by machining new dropouts.
I keep thinking about this too… However. Am I likely to play with chainstay length? If I know roughly what works for me already, am I likely to want to tweak it much? Also it would add cost (though decrease complication of build slightly), a small amount of weight, and those M8 bolts are never easy to undo once they’ve been done up for some time even if properly threadlocked!