Install position light bracked in right wing and pull string to fish wires later. For some reason, I did installed the bracket on the left wing, but not on the right. I decided to use nut plates for this bracket because the nuts were so hard to install on the left wing. If I remember correctly, one of the left wing nuts took me almost 2 hours to get on the bolt. This went much smoother.
For other builders, I'd suggest installing the brackets before installing and closing out the wing tips.