I riveted the bottom rib together tonight. The rib is formed in two parts, one on each skin, and then riveted together. I started by riveting the aft-most 8 rivets on the right skin, For the aft-most two rivets, there is barely any clearance. Some builders use very thin bucking bars, but it’s easy to make a mess. Given my skill-level, I took the safe option and pop riveted the last two holes. These are counter-sunk pop rivets, and when the airplane gets painted, they will look just like the rest of the rivets. 
Then I pop riveted the two parts of the rib together with 11 pop rivets:
These turned out to be a real pain, especially towards the aft end. I fabricated a “wedge tool” to act as a shim, allowing the rivet puller to angle away from the rivet, but still have the rivet head be flush with the surface. Several of the rivet shafts snapped off part way down the shaft, instead of flush with the rivet head. I trimmed them with side cutters, but it is frustrating to have it happen. I don’t know what I’m doing to cause the issue, I’ll have to do some research.
Then I clecoed the rudder horn brace, but didn’t have time to start riveting this tonight. It was a very tight squeeze, but I eventually coaxed it into position. 
This afternoon I stopped by a fellow Chapter 338 member’s shop to check out his RV-9 build, and to borrow a 6 foot long bucking bar. It was a super helpful visit, and I picked up some good tips. The bucking bar is to back rivet the rudder trailing edge, once I finally get to that step, hopefully this weekend.
