I think the range of schools you listed are realistic.
It really comes down to choosing which schools you feel you'd fit in best (or the ones you'd love to go to the most) in each of these groups.
For the stretch schools, I'd limit it to 2-3. Kellogg and Tuck tend to attract more consulting/general management types (and relatively fewer folks wanting to do finance), whereas Booth and Columbia are going to attract a very large chunk of folks who hope to do finance post-MBA. That will certainly influence the culture of the schools a lot.
As for the sweet spot schools - I'd limit it to 2-3 as well. Darden is pretty hardcore in terms of workload (and out of the group, will attract a more "serious" kind of personality). NYU, UCLA, Michigan and Haas are known for being pretty laid back and easy going - with folks really clustering regionally around the school (i.e. NYU grads tend to cluster in NYC, UCLA and Haas grads will tend to remain in California post-MBA, Michigan folks will stay in the midwest and/or northeast).
As for your safeties - it really depends how risk averse you are. If you're willing to take more of a risk (i.e. apply to say 3 sweet spots, 2 stretches), you may only want to apply to one safety. In any case, with the range of schools you listed you should be able to get into at least one school, assuming your applications are well executed and you don't run into really bad luck.
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