Hi! I had an ms composit UNIQUE, which most likely uses the same building techniques, and cruddy instructions. On the UNIQUE, the string was used as a spar for the wings, and for the fuse sides as well. If I recall you are to cut a slit in the wings where indicated in the instructions, then push the string into the slit/slot, and finally fill the slit with CA soaking the string. Same operation on the fuse. Good luck bmoran!
Trevor