The spar carry-through from the RW8 plans... Front view and side view. The spar carry through is a 3/4x2 wood piece, with a 1x1x1/8 inch aluminum U channel over it. You are then to insert two AN3 bolts edge-wise through this for attaching the cabane tubes. An AN3 bolt is 3/16 inch in diameter. That would result in the wood (on each side of the hole) being about 0.281 inches thick, or only 1.5 hole diameters. Other than the obvious problem of making sure everything is straight before starting your drill press, are there any other potential problems with this? I think it would be better to drill the holes through the 3/4 inch thickness, and attach the cabanes to the front of the spar carry through.