I started this session by doing some final test fitting of the lead counterweight that will need to be installed inside the top of the rudder. I needed to countersink the two screwholes in the weight in order to allow dimpled holes to fit into them, but I found using the hand-operated hole deburring tool easier than setting up the machine-countersink. I also needed to remove a little material on the sides to allow the existing rivet shopheads to not contact, but a round file was good for that. Once I was happy with the fit, I mixed up a small batch of tank sealant and applied it to the bottom of the counterweight (based on some thread discussions on VAF) and then screwed the weight into place with its backing plate.
With the counterweight installed, I could now cleco in and then rivet the top rib of the rudder. Six of the rivet holes needed to be upsized slightly to accommodate blind rivets, but the rest of the holes with just simple flush rivets that I could install with my hand squeezer.
Finally, I installed the several dozen flush rivets along both flanges of the rudder spar that attach the skin to it. As I was installing these rivets I was inspecting carefully to see if there was anything of concern based on the recent laser-cut hole drama that was particularly affecting the spars of various parts, but I didn't notice anything unusual.
What's next? I just need to squeeze the double-flush rivets on the trailing edge, and then curl the leading rounded edges and then I'll be done with the rudder.