Yeah the medium. I would happily ride this for CX stand over wise. It grazes the inseam of my trousers but I can lift it a couple inches before it hits bone. Thats with a 28mm tyre btw. A 35mm tyre would raise it about 0.5cm afaik. Could have gone with the small for a more road oriented build with a 10-12cm stem but as I’m considering some off road use wanted to minimise toe overlap risk and as am also considering flat bars (mainly to avoid getting into expensive brifter set ups but still be able to use hydro brakes) I went with the medium for a longer tt.
Best to check his cycling inseam/stand over with book in crotch method.
It’s basically the same geometry as a traditional 54cm road frame (54cm seat tube x 54cm effective top tube) which I have and which I know fits me with drops with an 80cm stem and flats with a longer stem. Except that because it’s a semi- sloping top tube the front end of the top tube is a bit higher and the back end (under the nose of the saddle) a bit lower than on a traditional horizontal top tube frame. But the stand over at the mid point is basically the same.
Next step is to get forks (the ones I tried for sizing are rim brakes only) gave seen the dawes galaxy ones on eBay going cheap but not sure about their tyre clearance. Have kaffenback ones but as this frame set is replacing the kaff probably want to keep those with the frame and sell together.
I was going to build an xs one for my tiny dad as he wanted something lighter than his 70s bikes but still steel, but he’s only gone and bought a full carbon rig to help prop up his lbs!