I first installed the shells on the connectors where they were missing. I then could clamp down the harnesses on the subpanel.
The picture shows the two C-clamps and on the left one of the d-sub connexions.



I then finished wiring the intercom and the audio mixer. I also modified the audio output wiring of the GPS, this will allow for easier rewiring depending on the outcome of the investigation on my GPS (answer in a few days).



I will have to modify the support bracket for the clamp that will hold the harness as it routes trough the rib hole, the wires might chaff against the hole edge.