The primer on the practise kit parts dried to a nice tough finish. Flexing the skins had no side effects, to that end rolling the leading edge of the practise kit was no problem for the primer. It was also quite resistant to scratching.
With the primer test now out of the way, I assembled the practise kit. I accidentally used -4 rather than -3.5 rivets in two positions on the spar flanges, and had to drill one out. The last rivet closest to the trailing edge on each side was a pain to buck. Otherwise, the practise kit went together easily.
After finishing the rolled edge closeout, I wiped the completed kit off with some acetone, and then dropped it by accident, denting one end of the rolled leading edge. Moral of the story: an assembly is not finished until it is wrapped up and protected from accidental damage.
Finally, after many months, the workshop is now ready, the practise kits are done, and I can get back to finishing the vertical stab and moving on with the rest of the empennage.