1 question to those who have already assembled.
The saddle elevation on the handlebars is extreme due to the negative stem. How are you coping with it? Otherwise it was 9 cm, with a spacer I am 15. I also don't want to undercut that extreme.
2nd question .. do you have a disc in between or was that how it was?
I think the 3.5cm of spacers that the frame comes with are about enough for the steerer safety - if you need more, it may be that the frame is too small, or that the frame's geometry is not good for you/your needs. For instance, I ordered a 56cm (182cm), which would have been aggressive but still "friendly", but I received a 54cm by mistake, which is fine but with a 2cm shorter head tube making it much more aggressive.
About the disc, it doesn't look like it belongs there. What's the purpose of it?
Assembly from the bottom-up: fork, fork race, bottom bearing, head tube, top bearing, compression ring, headset cover, (spacers), handlebar. Obvs the expander plug goes in the fork steerer