Remember that each woman has a different experience. Some women have such a light period that they only notice it because they find spots in their underwear. On the other hand, a woman with endometriosis will probably start being in excruciating pain the day before the period starts and will know exactly how long it lasts.
Source: I know someone with endo. She also has a resistance to at least one OTC painkiller because she used to pop those things like candy. And a female coworker of hers (with a very light period) thinks that most women are exaggerating and that periods aren’t much of a problem…
Just stagger the classes not just by size and/or weight but also by motor type. For instance, a tax class for ultracompact cars could look like this:
(I basically went with Japan’s current definition of kei cars and replaced the displacement restriction with a weight restriction.)