That seems reasonable, but at the same time it does sound like there would just be a disproportionate difference between the bottom and top levels. I can see ho

That seems reasonable, but at the same time it does sound like there would just be a disproportionate difference between the bottom and top levels. I can see how gray area mixes would require more careful calibration. One way to do this would be to look at your best and worst (group) cases and set the ranges according to those numbers. Having a fixed budget makes planning a lot easier. Probably more difficult if the budget is more fuzzy.