The main skin of the ailerons go together pretty quickly, and being able to back-rivet all the stiffeners and end ribs makes it rather easy. Riveting the top skin to the spar also went together really nicely, using a bucking bar that is slightly angled such that it can rest against the far end of the spar flange. I used some spare j-channel and clamp-style clekos to keep the trailing edge straight while riveting the skin to the spar.
The big oops moment here was that due to the counterweight in the leading edge being the significant portion of the mass of the part and the counterweight only extends about 2/3 the length of the aileron it is very heavy on one side compared to the other. I had the aileron sitting square in the cradle, which was positioned at about the 1/3 and 2/3 points lengthwise. When I got to riveting the very end of the (heavy end) of the top skin which was extending outside the width of where the cradle was positioned. The added weight of the bucking bar and the forces of riveting caused the the part to be come unbalanced and the opposite end of the part to lifted out of the cradle. This caused the location where I was riveting to drop an inch or two before I caught the part from falling out of the cradle, but unfortunately caused the rivet gun to pound the delicate skin once or twice on the way down.
After some cursing and swearing, I decided to drill out all the spar rivets attaching the skin, and assess if I could flatten out the dent I had just made. I purchased a set of dent removal punches from Amazon, and spent half a day tapping and pounding on the dent. In the end, I was able to get it pretty flat, but because the material was so thin, it had become even thinner in that region and was oil-canning in or out. In reality, I probably could have just used some filler and painted over it in the end, but it bothered me enough that I didn't want to keep it. Especially since it was on the upper surface of the aileron and I know I would notice it. I ordered a replacement skin from Vans, and proceeded to drill out all the stiffeners and ribs from the skin. I was actually surprised how cheap the new part was, I assumed since i was so large that it would cost a ton for the part and shipping, but it was only about $25 shipped since it could be rolled up. If I had known that up front, I would have just ordered the part immediately and had not bothered at all trying to repair the dent.
The next challenge was the end ribs. These required AN470AD4 rivets, that in particular on one end had almost no space to work with on the forward side. The space was limited by the two hinge brackets, and I puzzled a bit on how to get a rivet in there. If I put the manufactured head on the aft side, it would be possible to get a really narrow bucking bar between the hinge brackets, but I would need a rivet set that was a solid 18" long to reach; and I didn't own such a rivet set or bucking bar. If the manufactured head was on the forward side, the rivet set was too large to fit between the brackets, and even if it did, the rivet holes were not centered between the brackets.
At this point, I had to consult the internet from build logs of other fellow builders, and thankfully some good solutions here. In the end I pulled out the angle grinder and ground down one side of my offset rivet set. I hate damaging or modifying my tools, but I figured the tool isn't that expensive if I needed to replace it, and it likely would function just fine after the modification. In the end this worked really well, and I think the rivet set still functions just fine for future use. The only down side was that getting it aligned was still rather challenging, and I did make a few small smiley indentations an almost all the rivets, but to the best of my knowledge it's cosmetic, and I buffed them out and moved on.
The plans call for aligning the "D-cell" of the leading edge to be square before closing it out by riveting the bottom skin. I used a digital level and a short piece of wood as a straight surface to reference against the skin. After going from one end to the other probably 50 times I realized that the skin was fundamentally too flexible to give any reading more precise than about 1 degree, so I finessed angles by torquing the leading edge as best I could within that threshold.
Riveting the bottom skins was definitely working in confined spaces. I have fairly small hands, and I don't see how anyone who has large hands could possibly do this. The bucking bar that I had only squeezed between the flanges of the spar with about 1/2 inch of working room, and the top and bottom skin press together pretty tightly to make this a pretty tedious job.
Last was the trailing edge. I reused the 3D printed jig that I made for the flaps to countersink the trailing edge, which worked like a charm. I'm not sure if I mismanaged my stock, but realized I only had a single piece of trailing edge that was long enough for the entire part. For the right aileron, I had to join 2 pieces together. Since this was already in the plans for the flaps, I didn't have a problem doing this here.
Riveting the trailing edge was done on a back-rivet plate. I simply used the largest diameter back-rivet set I own, and drove the shop heads all the way down to the material while trying to avoid damaging the skins with the rivet set. With a little practice, this worked pretty well and the manufactured heads ended up pretty flush with a surface finish that looks pretty reasonable to me.
The final product came out quite straight, as about as square as my digital level can sense, so broadly speaking pretty happy with the part. Now the attention goes back to starting the fuel tanks that I've been putting off!