It took me a little while to convince myself what to rivet when. I finally decided on this: rivet 6t3-5 (lower horn) to 6t3-6(horn doubler) inset that assembly into the skin and rivet that to 6t3-7 and the two rivets in the back of the skin. then cleco on the upper horn and stiffeners then insert the ribs. Finally insert the 6t6-3(elevator cutout channel) and the hinge and trim tab skin.
Now I just have to do the final alignment of the stab and the elevator, and safety wire the hinges.