Yeah, top access would be a PITA. My bed can supposedly come apart. But that involves putting the mattress somewhere, and each bed section is heavy and very difficult to maneuver.I love the side opening battery box. Was planning to put my batteries in similar location but didn't want to have to pull the bed apart to gain access with a top loader.
I was thinking of that but that locks the wires in place. Might do that once I'm satisfied with the wires. But the housing itself doesn't seem to have any rubber, it's just clamped to plastic. So I'm not sure I'm letting in more water especially since it shouldn't pool around the wires.You might want to consider adding a blob of silicone or some kind of sealant on top of and around the grommets. Water seems to be able to get in via the smallest of gaps. Especially when aided by gravity. At least that's my experience.
I think silicone can be peeled off fairly easily. I've had to remove some from a bathtub. Maybe ensure there's a "dip" in the wires before they enter the van. Water could flow along the wire.I was thinking of that but that locks the wires in place. Might do that once I'm satisfied with the wires. But the housing itself doesn't seem to have any rubber, it's just clamped to plastic. So I'm not sure I'm letting in more water especially since it shouldn't pool around the wires.
The channel bolts all work when tightening from outside the strut, but when tightening from inside, the nut tends to turn and the grooves come off until the nut is parallel with the strut. I could use a washer, bit would need to be quite thick and just the right size.The strut nuts should have grooves to pull tight against the lip of the upturned strut. May have to hold them in place while starting, but once pressure is applied they should bite. They're designed to hang things from the open side so you should be able to attach your top piece either way since your first runs are turned up.
I'd get a right angle attachment for your drill or a low profile ratchet with screwdriver bits so you can remove the black panel if you need to change the taillight. Looks like you have enough clearance.
I wouldn't use silicone until you're ready to finalize, it sticks pretty good and nothing sticks to it, so you really need to clean it off if you want to redo it. I don't have a trick to move the middle of wires without undoing an endpoint, but if you figure it out I wanna know.
Edit: Actually, if the wires are just laid in the strut, you could flop them over the side and ziptie to the side of the strut facing the center of the roof. Any excess could be collected too to reduce visibility.