I made the two 1- 7/16th blocks for the centre section, where the wing retaining bolts will go. This helps to hold everything straight and true. The 1/4 holes in the wood, I enlarged to 3/8ths so the wood wouldn't 'grip' the bolts. The 'beolube' helped with the bolts, and a very gentle tap with a rubber mallet.
I bolted and clecoed the two halves of the centre section using the 1/4 bolts, and clecoes. I then drilled the rivet holes to full size, as well as the rivet holes for the nutplates that are on the 'top' surface of the centre section. These will rivet the two parts together later.
