Pinning them would the best option, I would (as I have done many times) replace the plastic pins with metal.
You can use brass rod, drilled into the wing. If the hole in the fuselage is too big, you could glue a bit of brass tube in there and make a nice slide-fit with the brass rod dilled into the wing.
Albion makes a series of slide fit brass tubes, they come in handy for these jobs