I finished building my "prefab" roof. I went shopping for some 16 gauge wire at Lowe's. I noticed they had 100' long 16 gauge extension cords for $16. This was a lot less expensive than spools of wire. I used the extension cord for all of my wiring. Less expensive, easy to use, and safe. I also installed the 1.5" of insulation between the spars. The ceiling is covered with a textured FRP panel.
It certainly was a lot easier to build the roof on my work table. I will build the curved front section separately.