Looks to me as though it's standing a bit proud on part of one side and by the screen. It's going to take some skill to getting that to look good before paint. As Rich says now I've seen that glue isn't the answer as it will need something else as well.
Does it flex at all at the split if you apply pressure to different parts of the wing?
I've only worked with fibreglass on my ponds so far from any sort of expert but that would have to be cut larger and deeper then built up with fibreglass and resin, then gelcoat. Then it would be able to be sanded and blended.
It would also give you chance to dig away any filler that is underneath to put some sort of strengthener and bound to chassis if needed.
GELCOAT FILLER is a white, waterproof gelcoat filler for surface repairs. It is paintable, easy to mix, apply, shape and sand. Suited to marine paint, can be pigmented or painted with any marine paint. Use with glass-fibre Mat for structural repairs to GRP and can be used on glass-fibre or gelcoat. It has a working time of 8 min and a curing time of 20 min. Can tolerate temperatures up to +160°C and contains 432g/l solvent.
And then i can use the fibreglass on securing the wings or reinforcing other areas.