I finished up my rudder today. The skin was already drilled, so I aligned my ribs (including the base rib attached to the rudder horn) and drilled them. Took it all apart and deburred the 3/32" holes, then reassembled and updrilled to 1/8". Took apart again and deburred everything.
I then riveted the base rib/horn assembly. I had one poorly pulled rivet, but it drilled out easily and the replacement sat great. Then riveted the rest of the rudder together.
There was some interference between the longer CCP-44 rivets in the horn assembly and the CCP-42 rivets in the skin. I angled the rivets in and used the EAA/Peter Buck wedge & angled mandrel method to get them to set correctly, and all of them came out perfect.