Ben,
That black stripe is whack, and should be fixed if you continue to use this form, but imo, your test form does not allow you to analyze the entire sheet proficiently.
Often times, test forms don't necessarily reflect any typical press run. For example, the average amount of coverage per key, per ink channel. Most test forms I've seen have too much coverage throughout. For that reason (and others), I've created this file, because it approximates per channel coverage a little more realistically (up for debate, for sure, but typically I see 20-30% coverage from lead to tail, per key, per channel on average). I also like its simplicity, even though there are occasions where I need additional targets added to the set. That said, of course, on any given set sent to press, TAC will vary a lot. But that doesn't negate the usefulness of this test form.
We then multiply this file many times up, without any other files, throughout a set. It allows you to measure solids pretty darn close to where you can measure TVI. It's also pretty good at revealing possible issues at press (i.e. chatter, phase, slur, etc.).
Give it a try or use something similar. You'll "see" things more clearly, as has been my experience.
For example, I like to keep SID from lead to tail within 5 points and consistent from left to right.
And if I ever measure TVI fluctuating greatly, I might discover slur, dot doubling, striping issues or gripper issues as the cause.
Although my comments are only a brief summary of a more complicated process, I hope this helps if even just a little.
