<snip>Do you fully sheet the wing first? Seems that would defeat one of the reasons to fiberglass in the first place, that being that it is lighter weight than shrink covering. <snip>
After reading the original post again, I'm wondering if JollyPopper is confusing the use of a fiberglas fuselage with the practice of 'glassing a sheeted or planked structure.
A fiberglas fuselage is usually lighter than the corresponding former-built balsa/ply fuselage, covered with film or fabric. There are tradeoffs, in building technique.
A balsa fuselage or sheeted wing, covered in fiberglas and painted, would seldom be lighter than the same structure covered in film.
Just a thought,
Dave Olson