Doesn't look like a tapered/44 head tube though, which restricts your options to use a Modern fork. I don't necessarily think that it needs it, as if you're happy running rigid for good then there is no point, just sayin'.
44mm would have solved it. I have a Ritchey WCS rigid fork on my steel frame with 44/44mm headtube. Since the diameter of the top of the carbon crown matches the HT diameter, it looks neat, even with a non-taper 1 1/8 !