Before riveting I cleaned and sprayed some self-etching primer into the inside of the elevator horns since the powder coating doesn’t cover this area. I probably spent more time trying to peel-off the stickers. Not sure what adhesive they use, but it is robust.
I had read a few posts where people had difficulty in aligning the final drilled holes for the elevator horns after riveting the front spar and root ribs. I decided to do the final drilling after riveting and didn’t see any issues. The first time I clecoed them, it did take a little coaxing to get the first few holes to line up, but once a few of the clecos were in place the rest of the holes fell into place.
The next steps are to rivet the ribs and gussets to the rear spar and then back rivet the assembly to the left top skin and right bottom skin. I spent some time laying out all the ribs and spars to make sure I got the right ribs onto the right positions.