Yes I think my flat mount is less "flat" than dsaul's. I made it by modifying a post-mount dropout (described in this earlier thread):

Flat mount caliper-- how big should the holes through the chainstay be?

But basically the casting I have slopes up a bit more, creating the issue. Possibly also because it's QR rather than thru-axle.

I have the DR03 from here. dsaul's looks similar to the DR06:

https://www.framebuilding.com/NEWPAR...20Dropouts.htm

Also dsaul has an adaptor there for his 160mm rotor that raises the caliper up a bit. My rotors are 140mm (not about to change those

The cable stop seems to be aiming slightly at the inside of the CS. So it's possible that I want to run a bit of outer inside the CS and then along the bottom of it. Then maybe I put a cable stop a few inches in on the bottom of the CS (just like the one that's on the other side for the rear derailleur), run bare cable under the BB shell if it will fit with the gear cables (or perhaps route it above if not) to another cable stop somewhere. I will experiment tomorrow also with the wheel in there to check how things fit.

Slightly tempting to run a bit of 3/16 pipe through the CS and out of the bottom, having just watched Paul Brodie's "Mantis stem" video But I don't think this is really a good idea.

Although this is a "gravel" bike I expect it to be mainly ridden in the quiet countryside around Berlin and I'm going to be running the gear cables in segmented sections anyway.