On the wing - it looks to me as if you were better off cutting one (or both!) tabs off and just using those large flat surfaces to glue the parts together.
In the photo above something is interfering with the fit and I could bet a small amount of money it's one of the tabs (or both). Maybe it would be a good idea to narrow the tabs down (chordwise, so to say) or at least make teir sides taper - that could help, too. Once again, in the photo above if you could move the left part "down" (towards the bottom of the photo) it would not only take care of the panel lines in the top portion of the photobut also make the gaps smaller.