As others said, RTV is no good. I would use a DAP sealant today and not mess with the ProSeal on these lights. The stuff is flexible, paintable and you can easily wipe it off before it's cured.
The wing tips have always posed a mystery to me. With such a beautiful and sophisticated design WHY did Vans leave us with that horrible meeting of wing skin and wingtip near the leading edge!
I ended up cutting off some skin and using Bondo to get a smooth edge. (After it was licensed ELSA)