Thanks, that did the trick!
Your solution actually worked better when I removed the Sort Parameter and simplified the Rank Filter to just "if index()<= [N Customers] then 'yes'". Adding additional sort controls based on a non-plotted calculated value doesn't play well with Tableau's built in sort button, unfortunately. In this case, the using the Rank Filter and Tableau's sort button appear to be sufficient.
For any future readers of this thread, my solution (based on Aaron's) is attached.
Thanks again, Aaron!