I use them on all my machines, well I just have Feed and spindle overrides, I link the Rapid To FRO in General COnfig and the pot acts on both, turn down FRO and rapid is also turned down.
I input the analogue signal either via a PLC or on the wee lathe I am doing it goes via the CSMIO controller as it is capable of analogue inputs.
The other option you have for this is via a Pokeys as it has 2 analogue inputs.
Like you I find the FRO invaluable for testing code on a first run, especially on the lathe, turn it down as you approach the material and get ready to wind to zero if it looks like its going wrong or wind back up if it looks right
Hood