It is not only total utilization but utilization on each card and number of cards with a balance. If the only thing changing month to month is your utilization then you should be able to figure out your sweet spot by comparing your CR's month to month.
That shouldn't be an issue for me either. My primary spending goes on a business Amex CC. My personal cards constantly maintain a very minimal or zero balance.
(Besides, that sounds like a pretty dumb way to determine risk imo... spending more on one card vs spending that amount on multiple cards.)