After figuring out a workable method on the right elevator I thought I’d show some pictures of my method on the left one. First I cut reasonably close to the line with my bandsaw. Then I trim up to the line with these offset Wiss snips.
I cut the corners with my Dremel tool.
I do the holes for the ribs using my handy rivet spacing tool. There is a warning specifically saying not to drill through those holes (use it as a layout tool instead), but I have totally disregarded the warning. Hopefully whatever bad outcome I receive by disregarding the warning is offset by all the time I save.
I also attached the hinge to the right elevator. This needs to be positioned such that it will line up with the rest of the horizontal stabilizer when it is riveted together. My yard stick seemed to be just the right thickness to use as a spacer and get everything lined up.