Hi Rate1
Some people that is sheeting with vaccum is not edge glue the balsa sheets at all, but are mearly tapeing them together as it all is going to be laminated anyway.
Methinks I would joint the sheets first (using a strip of masking tape along the joint) using Aliphatic Resin glue (looks like PVA or Evostick ResinW only yellow)...not CyA. Any excess glue can then be wiped off with a dampened kitchen roll tissue sheet. This way you have control and there is less likelyhood of error if the sheets become separated in the vac bag. When dry, you can then sand the sheets flush and trim (slightly oversize) each panel noting which is the best side of each sheet so that goes on the outside.
Tape two sheets together with several short pieces of masking tape acroos the join to pull them together and then add a length of masking tape (pref. the Blue stuff from 3M) along the whole length. Then fold them along the join to expose the edges..then apply the glue sparingly along the joint...then fold flat again. Wipe off the excess, then add the next sheet(s) likewise. Lay on a flat surface (tape down) and cover with film backing sheet or clingfilm and weight down with a few of your old magazines. Leave overnight to dry. Remove the tapes and lightly sand off the surfaces flush. Trim to slightly oversize (maybe 1/4 to 1/2 inch) then its off to the vac. bag with the whole caboodle. Good luck.
Cheers
PS
Maybe take templates of the root and tip of the wing cores..If you upscrew, you can then maybe get new ones made locally...you may have a problem with the joiner tube holes though...got to be some skill in removing those from a core!