Frame received a few weeks ago. Built with Dura Ace and Campagnolo Bora Ultra 60 wheelset for a total weight of 7,12 kg. The bike is insanely fast (coming from a 2009 Cube and a 2014 sub-6 kg Focus Izalco Max 0.0). Stack is indeed very low, I almost wanted to ask for more spacers but ended up with just the standard 6x5mm spacers. It's an aero bike after all and that would have been not really nice aesthetically. I actually feel very good on the bike now, quite comfortable. I had some issues with some screws and engaging the thread in the nuts (used a tap to clean the threads). Another issue is that I have to apply a lot of torque on the headset to remove any play (there is enough space between expander and top plate and bearings are not compressed at all). I'm guessing it's because there is a lot of friction between the fork and stem. Headset fine tuning was not easy, but maybe I'm just bad. Really happy with the frame regardless.
The frame came with both a steel bolt kit and a titanium bolt kit.
I suspect the titanium bolts are from S-Parts, a brand commonly used by bike shops in China.
While they aren't cheap, they do seem to suffer from occasional QC/tolerance issues.
The steel bolts thread in perfectly, but some holes felt a bit tight with the included titanium ones.
In particular, the M6 × 15mm bolt for the seatpost wedge clamp wouldn't thread in at all when using the provided titanium bolt.
Switching back to the included steel bolt—or using a titanium one I bought separately—worked flawlessly.