Got the bike more or less completely assembled, just missing a few non-vital parts like bar tape and proper bottle Cages. Here's some findings.
- The headset dust cover/top cap is hitting the frame (even with the C clip included). I made a small plastic C-shaped 0.5mm thick spacer and that seems to do the trick so it clears the frame (at least so far).
- The fork just slightly scrapes the bottom of the head tube (see attached picture). I'm guessing it might be hard to space this out, so probably going to sand the bottom of the head tube a bit so it goes more clear of the fork.
- The chain stay issue that Patrick also showed seems to be also present with Ultegra R8150 rear derailleur - I have not played around with chain length yet to see if that might change things (if someone is more experienced than me with B-screw vs. pulley wheel to cog clearance vs. B-screw I'm open for input). Basically you seem forced to have the B-screw tightened more than needed for the RD cage not to hit the chain stay. I couldn't get the ZTTO SLR Gen 3 11-32 cassette to shift well (it shifts OK on two other bikes here) as the cage cannot be moved close to the cassette, which seems pretty important for that cassette to work. I've put on an Ultegra 11-30 now and that seems to be better in the stand at least. You can see on the attached pictures how close the RD cage is to the chain stay currently, yet it's still quite far from the biggest (30T) cog on the cassette. If I loosen the B-screw to bring it closer to the biggest cog it will hit the chain stay in the smallest (11T) cog.
Unless I find a good fix for that last issue it is a bit annoying as I think it's quite the oversight in the frame design - and a bit surprising considering this is not their first frame. I know they've fixed it already in at least some of the sizes, but it seems they've also shipped some frames out with this issue after they became aware of it.