I have a bit more data from Dassi. The bottom bracket in the frame is "Aerospace grade alloy. Machined in two interlocking halves and bonded in". My size for the Dassi would be a 54.
The geometry of Dassi would be ok except I will need around 3 cm of spacers as I'm too rigid for a 54.1 stack; I need around 57. Any advice?
Now - the 2 carbon bikes I am contemplating are Crumpton and Dassi. In short, the aesthetics of Dassi are hard to beat (de gustibus non disputandum est) - it looks almost as good as a titanium bike (joking).
However, the Crumpton is custom made and I can build it so I have no spacers or just 1 little spacer (2-3 mm). Their bottom bracket is (threaded) titanium - that's a statement of no compromise quality imo.