That's how I did it with my X75 many times:
This way I can run the JVC PJ calibration with no risk of overriding the existing calibration in the PJ:
When it comes to the point, where the JVC SW shows you the result, don't click on SAVE before you have verified the result using any other measurement SW (LightSpace, CalMAN, HCFR, CP ...).
If not happy with the result, just click on CANCEL. Only with SAVE the new data will be stored at the PJs flash memory.
If you choose CANCEL, and you want to get back the old calibration, just switch over to any other color profile and change the Lens Aperture setting by 4 steps (eg. if set at -4, go to -8 -> this will restore the Color Data from flash). If you only want to get back at the Gamma calibration (still saved in flash memory), just switch between CMD ON an OFF.