I started on the trim tab today. I didn't end up doing much though, because it became apparent pretty quickly that my head just wasn't in the game. I didn't screw anything up, but I wasn't thinking far enough ahead to keep from having to stop and redo something that wasn't mentioned in the plans but that I should have done. The instructions are getting more and more sparse at this point, so you really have to think through how everything goes together before you start on a step.
I clecoed the trim tab to the Z spar and then squeezed the trailing edge per the plans. Basically, they have you squeeze the edge little by little to flatten it out so that it's a straight line from the edge to the spar with no dip or puckering.