Technically this is two days, because a couple of days ago I riveted the gusset on to the rib. What a pain -- over an hour and about 6 drilled rivets later there were 2 installed rivets. Some fool posted on their site that out of 15,000+ rivets, they only drilled out 200 or so. Calling BS on that stat...
Today was just a bit of time on the plane. Riveted the bottom skin to the E-901 spar, then attached the Counterbalance assembly to the spar. This is the reverse order of the instructions, and works out better. One pair of rivets buried way down inside connects the counterbalance assembly directly to the spar. I used (gasp!) pop rivets. Out of site, just as strong, and the result is a much better grip than trying to get in there and buck a standard rivet.
Next up will be the trim tab spar. But I need to go heads down on work for a week or so, meaning that all progress will stop for now.
Total time: 1.5 hours