While there are no settings to handle middling natively in ranking system nodes, you can use formulas like this: Abs(CapExGr%5Y - FMedian("CapExGr%5Y")). This formula will fold values around the median, so Ranking would need to be set to Lower values. (CapExGr%5Y is equivalent to the deprecated factor CapSp5YCGr%.)
Is this a workable solution for you?