It is just one of things my Dad taught me before that you don't tap and thread plywood. It doesn't hold the threads as well as solid maple or oak. The only doublers are the ones for the hold down blocks. I don't thin my epoxy as I will want a stiff mix to pack inside stab/fuse joint. I use finishing resin w/ micro bollons for fillets and again I won't thin it. I may try some micro filler from NAPA that a scale modeler uses in a scale build thread "Ramone Torres's 1/5 scale T-34 by VBDRIVER" for the fillets. It is supposed to be easy to sand. I know I show a lot of GP products in my pics. I hope the moderator don't mind. I'm lucky to have a VERY WELL stocked LHS a few miles from my house.