Dear Luis Speaking about the filler blocks: " In my case, the plywood was almost 1/16" thinner than 3/4". To compensate for this I will either use oak veneer or, as Steve suggested, I will build up the Epoxy glue to fill the gap". I 'm not a pro but perhaps would you better ask to Peter M Bowers. Filling the gap with epoxy will not give every garantee of solidity in this area ( you know, box structure , FAA inspector and so on...) . In France, some builders have made a mixture with sawdust and Epoxy with a poor result. Regards, Jean-pierre Nguyen