Found the #2 angle that mounts the channel to the rib was the wrong one. Drilled out the rivets, elarged the holes to A5 to be safe and reinstalled. Used a chalk line to mount the spar to the table. Ribs were atached to the table. Center lines of the spars and ribs were marked. To line up the skin had to be moved 2mm forward to align. On the rear channel, the hole was lined up and drilled at each corner or the rear channels.