The method I regularly use is to have the twin wires built into the wing with the single wire emerging through a hole around 1/2" dia. I set the single wire to the lenth I require and then hold it in place with 3 or four short pieces of plastic electrical tape overlapping each other at the hole.

Looking at your picture, I reckon a rough but simple fix would be to tape the two floating wires down to the surface of the wing using the same type of tape....

Alan W