Just a quick session this evening to correct that one rivet on the first rear spar, and then I did the second rear spar.
I also ran over to Lowe's (I had a gift card) and picked up a long piece of steel to use as a back-riveting bucking bar. What I have is good, but I've made a couple of errors in the past because it vibrated off.
Looking at the next step, I'm going to need a long session--at least four hours, I'm guessing. So, I will probably take a pause until the weekend.