Thanks for the population numbers, I didn't know they were so different. I just ranked them from (my perceived) livability - SLC close to skiing/nature, while Minneapolis/Ann Arbor are not destination cities like the other ones.

I think Seattle / Boston can be T1, but then you'd have too many T1s. My logic was "do lots of people want to move to this city?" and I think the answer is "no" compared to the demand for the T1s.

I see your logic though, and maybe it's better to just have a T1 and T2.