200% would be good, on both the feed rate and the spindle speeds, for fine tuning out harmonics and vibrations and to hear what works best, as recommended speeds and feeds are often no where near the ballpark unless you have the perfect machine and conditions, most hobbists will never see. The option of adding aftermarket analog input potentiometer for feed and speed would be a great add on, alternatively maybe have an option to engage the MPG hand wheel while the machine is running a program, but instead of moving an axis it varies the feed or speed a certain percentage each click
