Unfortunately I dont have my boat anymore having sold it earlier this month, but if your set up is similar to that which I had on a B36(2002), all of the switches on the switch panel were numbered, and behind the panel looking towards the inside of the hull, there were a number of connections placed on a board located against the inside of the hull. Each of those connections were numbered, in accordance with the switches on the swing open panel door, and it is to those connections on that panel located against the inside of the hull where you add those extra items of equipment, not to anywhere on your swing open door. The connections on that board close to the inside of the hull are generally, if not entirely positive while a negative connection can be made to the long negative busbar located nearby.
Hope this helps.