OK, a few photos.
The first is the first successful install. This stands about 16' or so, and is really a bit too high, but about 6" below that the interior wall is sealed off to the attic and it is a difficult enough place to get to I did not want to try to dill and fish it to get the camera lower. A trim ring has yet to go on because I'm still incrementally patching the stucco from the two holes I drilled beside it trying to miss the studs coming in from outside; finally drilled from the attic out.
This is an outside view of my problem corner. The small hole is just above the ladder. The ceiling in the room next to it is actually higher than the beige and red band at the top of the wall.
I managed to get a cell phone pic by flashing its flash and the camera in the same 1" hole. This is looking up at about a 40 degree angle. The concrete in the shadow is the wall cap. The green styrofoam is a (required) tunnel that allows some airflow to the eve through the packed in insulation. If I run a flexible rod up the plywood beside the truss/rafter that you see on the right, it hits what I am guessing is the ridge board for the corner a bit less than 5'. When I looked from the attic I could not see it (I would be looking from sort of near the bottom left corner behind this view from about 15' away.
what I do not know is how much height is packed insulation before it reaches the level you can see in the attic, and whether I cannot see this rod because it is hidden in insulation still at the point it is stopped, or whether it might be actually up above the insulation hidden by a truss and I just can't see it.
But I can't see it. And every attempt at different angles so far gets me nowhere.
I may or may not be able to see light if shown through the hole, but at the moment my helper is rehabing an injured heel and doesn't want to get on a ladder. But one clue is I cannot see daylight along that edge, so it is pretty blocked by the insulation.
These are what the aluminum panels look like, this is some spare material I had lying around:
They are in narrow widths (by eye about 16" or so and lock into each others edges. While hardly structural they could certainly hold a camera when fastened on each end (as they are).
I'm about to go see if I can get one apart and get a bit better access. As mentioned above, aluminum bends easily but doesn't un-bend gracefully, so I have some worry about getting that "L" shaped piece away to free the panel up.
Final thought - I found I am about out of a box of interior cable that I thought was almost full, so I need more cable anyway. Thanks, Work2Play, for the pointer to the Ubiquiti Toughcable, I'll look at that, maybe I can pick up another 1000'. I don't want something too thick, as I've already put a 1" conduit in with plans to run all the camera cables through it to the switch. I tested and can easily get 12-14 of the regular grey cable, but anything too much thicker....