Now that all of the ribs and stringers of the Horizontal Stabilizer were primed, I could begin riveting these internal parts together into a basic assembly. The primary parts were the two modified inner ribs and the stringer web, and then bracing their sides with the two longer stringers. All of these parts were riveted together with round universal head rivets and squeezed with my hand squeezer.
Once those five pieces were joined, they could be connected to the forward spar, again with more universal head rivets using my hand squeezer. Some of the rivets were specified as using longer rivets where the spar doubler was penetrated, so I had to be sure to put those in the right places. After that, I riveted on more ribs along the outer sections of the forward spar, as well as just the two outermost nose ribs. (The remaining nose ribs will apparently be first riveted onto the skin and then blind riveted onto the forward spar later.)
I also spent some time treating all of the countersunk rivet holes in both spars with my alodine pen to minimize future corrosion risk in those holes.
What's next? I'm going to do some quick priming on the interior of the skins and then start air riveting the nose ribs.