Limits of functional parameters adjustable by a math channel or another functional paramater

I quite often use the sliders on my screens for a pump volume control. I connect slide to a functional paramater and use that to control the engine desired operating speed. Depending on the size of the plunger(these are changed regularly to adjust to pressure and volume requirements) of the pump the max volume changes a lot. So if we have a small set of plungers the slider has a huge range that is no longer usable due to the the max value set in the adjust group. I would like to be able to use a math channel to adjust the max value based on plunger size and max RPM. Maybe there is a better way of doing this though..