I’ve just build up a Croix de fer. Everything I read indicated I’d need a 60 cm but that seemed large compared with my road bike. I tested a 58cm Genesis Day One – very similar but not exactly the same geometry and went for a 58 Croix de Fer.
I’m 6ft 2” with a long upper body and arms. The 58 fits very well. Standover would be an issue on a 60. I’ve since heard Genesis CX frames come up large, I’d agree with that and suggest the 54 would be OK but try and test one of Genesis’ CX bikes if you can.
First thing I noticed was how comfy it is even with hard 32mm tyres but it’s not light even with my custom build.
Vin Cox rode a CDF around the world in the fastest time, then Mike Hall rode an On-One Dirty Disco around the world and beat that time – both would be good choices the DD will obviously be a lot lighter but doesn’t take a standard rack, isn’t as strong and the angles are a little more racey.