Vertical stab done
It took quite a bit of time to decide on a primer and get everything ordered and delivered, so I ended skipping through sections every time something was held up because it needed to be primed. Afterwards, I was able to revisit the vertical stabilizer, and it came together rather nicely without any issues.
Seemingly any time there is a rib with reasonable curvature, the plans calls to flute the flanges if needed. It isn't entirely clear to me when it's needed, as most of the flanges that I've come across seem to sit pretty flush with the skin after simply getting them at the right angle. Furthermore, all my attempts at using a fluting tool seems to just bend the flanges up and make it worse. Instead, I 3D-printed a little 90-degree alignment and bending tool that seems to work pretty nicely in getting the flanges nice and square. I'll try to put up a section to download all 3D printed tools I've come up with.