Originally Posted by
unterhausen
Do you overpack?
I think you already got your answer about the 1" fork, your builder said no. You're going to have to put in some research to find someone that will make one for you. Retrofit is out unless the existing fork is an overbuilt unicrown fork. Most forks built for rim brakes are very marginal for disc, it's not unlikely that it would fold under heavy braking.
The Ritchey fork has Axle-Crown: 393mm. Good news is it has 50mm rake, because that A-C is likely to push the front of the bike up and reduce the head tube angle.
I'm a little surprised I'm the only one who thinks you shouldn't put this much effort into major modifications on a $1500 bike. Does your framebuilder work for free?
I'm not sure it's worth it either and no, the framebuilder doesn't work for free!. My wife and I want Ultegra/GRX800 level components. The only cheaper (than the frame mods) but reasonable option here in Australia that I know of is the Norco XR Steel. It's a lesser steel than my frame, my wife has rejected the dull grey colour and I don't understand why a steel bike has a press-fit bottom bracket. Other options start around the same price as my frame modification but still not Reynolds 853 or equivalent.