I bought my Go-Power entry plate with a two wire pigtail lead, MC-4 connectors on one end and bare on the other.
The solar wires are stiff and do not bend 90 degrees, they require a fairly large radius bend so the hole under the connector plate should be offset from center towards the sloped front. Oversize the hole in the camper roof so the wires can enter at a bit of an angle and then bend the other direction (sort of a lazy "S" shape from plate entry to where they connect to camper wiring.
In this picture you see the 3M 4100 sealant around the edges (I also put it underneath the edges all around before screwing the box to the roof). The roof box is mounted under one of the solar panels.
I used high quality crimp butt connectors with shrink tubing to join the camper and solar wires.
I stuffed the wires back up into the ceiling here is a picture of the solar wires near the hole I drilled before I connected to them. You can see where they run above the styrofoam. Also you can see the locator hole in the aluminum plate under the hole I drilled.
Everything fit up in the ceiling above the styrofoam.
Here is a picture of an FWC roof frame (actually several leaning against a wall) showing an example of the aluminum plate with hole in it for solar wires. I think this is from a newer camper than my 2007. The front of the roof is up (top of picture) with driver side to the right
I also installed a small junction box which is large enough to screw the Solar Plate on the roof into - thus sandwiching the roof between the solar entry plate and the junction box for added strength for the Solar entry box. This was probably unnecessary because the 3M 4100 holds very well. I had to search an electronic supply store (like Fry' s in LA) to find a box the right size.
The cover on the junction box gave me a surface to press against when I patched (glued) the vinyl headliner). The horizontal lift board covered this all up. (thankfully).
The green surface is a thin piece of foam insulation I had and I used it to fill up the space.
I hope this is of some help.
Regards,
Craig