I would only work to make the step tablet patches about twice the aperture of my densitometer on the final film.

Because I am encouraging flare, I wouldn't worry about maximizing the frame. Also, I am satisfied with only a subset of steps for a flare test. I was going to be doing a "typical scene" kind of test. (But now it's hailing).

Backlighting a transparent test pattern is one good way to design a test that includes flare and also controls the lighting.