My support blocks are 2x4 stock also. Left over from some other project and had been cut down a bit. I just planed them square for this purpose. Good tip on drilling the ribs. Critical part. I have my ribs drilled n screwed together in 2 stacks, left n right. I have them pre-shaped a bit. My idea for the rod holders is a 2 piece holder east side. They will hold the rods then be screwed to each other then screwed to the support block. Work on one side of the wing then unscrew jig flip it over and screw it back down n work on the other side. The rods n wing will be held steady while flipping it over. Will see how it works out.