Going to preface this by saying I probably won't be getting this frame as I have the LTK266D-SL already as a test bike, and this bike doesn't do much that one can't other than be slightly more aero. This bike definitely needs the same kind of thread, though. As is, it looks like most people will need to convert to run a different bar/stem setup. There are also going to be a lot of challenges getting good info on tire clearance and saddle placement.
On the bar/stem front. This frame appears to use the "standard" 8.7mm bearing seat depth. This means that headset solutions from FSA, Deda, Token, Enve, Cane Creek, etc should all fit fine. Some of the lower-cost ICR headsets, like those from Neco, may not fit, as those use a 6mm depth. For bar compatibility, though, perhaps the more important thing is that it uses a circular headset cover, so the covers / c-rings that come with many bars are likely to fit and look good (not a comment on whether they are good quality or will work well).
As for geometry, the human body is complex, and there are definitely flat-back positions that work really well for people with good hip mobility but lower back issues. Those same people would find a more upright position to be uncomfortable. I think it's high time that we start to think about bike positions as requiring the right stack, not just higher or lower. That said, this specific sizing scheme is odd because it generally suggests that smaller riders rely on length to get the right back angle, while larger riders rely on drop. However, to counter the argument that people need more spacers, they then raised the stack, so the reach numbers get pulled in on the longer sizes while the wheelbase continues to grow.
I also question if this geometry chart is right; it looks like there are some reach/wheelbase numbers that would benefit from more scrutiny.
Overall, very interesting frame and I look forward to seeing some built up.
