Very frustrating day today. Clecoed the rear spar components together to find that on one side, the spar/doubler flange holes do not align at all - at least half a hole out. The next problem is to do with installing the rivnuts, either my brand new M3 mandrel is undersize or the rivnut threads are over size (or a combination of both). As soon as I start to squeeze the rivnut pliers, the mandrel strips through the rivnut thread leaving the rivnut free to spin in the hole. I managed only 2 decent installs out of at least 8 attempts.