Does anyone have a diagram of how the headset goes together? Is the top bearing, then that half circle thing, then the top cap and washer? That leaves a hole…
First the top bearing, then that half circle thing, then the washer (if necessary and you have to cut the washer to keep the hole for the cables) and then the top cap.
If you use internal routing (through the headset) I recommend to use FSA ACR headset.
Why? The half circle thing is much better with rounded edges and the top cap has a sealing.