Thanks for the advice so far but I think it's time to add some more info.

I'm building a Balsa USA Northstar. If you are not familiar it's a delta wing seaplane that is notoriously tail heavy. The recommended finishing job is to fiberglass the bottom of the hull then cover with either Ultracote or Fabric & paint. My thought was to cut lightening holes in the wing ribs, sheet with contest balsa then fiberglass & paint the entire plane. After playing around with fiberglass paint on the previous plane I'd like to try it on an entire plane and figured this might be the right time as it will seal the airframe as well as give a nice finish. Most of the people who have done this say it will make it come out really heavy but on the other hand I don't know there skill level with glass so it could just be that it was done improperly.