Hey BILLVO.
Congrats on picking up the Avion. I certainly love my 1987-30P. As far as solar power is concerned, I am in the process right now of adding solar panels to my Avion.
I picked up several 15w panels some time ago. I am going to permanently mount them on the roof, I actually think I'll begin with 3 - 45 watts total and see how well that supports the basics. If need be, I'll increase it to 3 more.
I am mounting them with aluminum angle run along the two roof seams, front to rear, then a second angle to attach the panels. Plan to drill and bolt the two angles together, then bolting the panels to the top angle. That well accomodates the distance between the two seams and the length of the panels mounting holes. I am going to run the wiring for the panels in 1/2" plastic conduit that will be clamped/bolted to the angle. I have a solar monitor panel/charge controller to install somewhere in-line, I think I will bring it in at the roof over the refrigerator area, mount the panel on the wall next to the refrigerator. Then go from the refrigerator area out through the floor, down the frame into the batteries.
I built an aluminum battery box that will house 4 batteries instead of the standard 2. Should be plenty of reserve power to run all the 12V stuff needed overnight, and then some.
Hope that helps you understand the needs to power up without worry. It will support running the furnace, refrigerator, lights, etc without ever having to worry about a remote boonie parking/camping.
Have FUN in your Avion.
CD