What I was thinking of doing was ripping the balsa wing joiner blocks in half just behind the 1/8 ply with a table saw. Add a piece of 1/8" aircraft grade 5ply to make up for the material cut out from the table saw and add in some of this (soaked in epoxy)
http://www.greathobbies.com/producti...rod_id=CSTC213 all sandwiched together with 30min to 1 hour epoxy. Pressed with clamps.