Help for custom Base board with the pixhawk 6X


I would like to build a custom base board for the pixhawk 6X.

I found the open specification of the connector, and the schematic standards on the github.

The specification for the 6X are not released yet, and still in draft.
There are many peripheral component to build the base board (µcIO, LEDs, RC).
Did you know if there are some design guide line to build a custom board available somewhere ?

thank you for your help.