The tip foam was some blue foam that an RV guy gave to me, I think its the standard FB foam from A.S.S. The foam was glued in place using Clearcoat. I used a panel saw to cut the bulk off, and then used Superfil Epoxy lightweight filler to cover. This stuff sands very easily, yet is pretty tough when you hit it. An orbital sander worked great for shaping. Two coats of Clearcoat were brushed on to finish. Fiberglass would be the perfect solution for this task, but I had trouble with that on an earlier attempt with the right wing, the Superfil method was a good alternative.
Although not on the plans, I finally decided to add corner gussets behind the spars on all the ribs. I then finally decided that I wanted to feather-in the 1/16 ply leading edge step that is created along the wing. I did this by gluing [System3 Quick Cure Epoxy] on 1/16 x 1/4 x 5 strips to each rib aft of the leading edge, then feathering-in with a block sander and Clearcoating twice.
I finished the final tweaks 1 a.m. Christmas day - a nice touch. The port lower wing is now done!
Now I plan on the relatively quick task of adding the corner gussets and feather-in strips to the starboard wing, then I will start planning for Big-Bertha - the 24ft upper wing...