I now have a X75 and can also say, calibrating the grayscale/gamut isn't the problem (using a video processor like the Radiance).
Unfortunately I have (had) some other trouble. My former JVC (X70) was pulsing in high lamp mode + using CMD. Got told from service, that's no failure, can't be solved.
My replacement-X75 (not for free!) has a terrible native convergence; red+blue starts shifting from the screens center till the right / downside borders. At the end red is >1 pixel off. And every time after power on the lamp flickers slightly for 1,5h ... 2h, until it becomes maximum operation temperature.
For the last point I'll go in contact with the service. For the first point all JVC users have to live with, because JVC's are equipped with a digital pixel adjustment to "correct" convergence issues (but not w/o side effects
I really don't know, if my next PJ again is a JVC. Too much qualtiy issues. But to be honest - the nativ contrast ratio and nativ "black" is great, and this w/o dynamic iris aperture. Also the native sharpness (despite of the convergence) is very good all over the screen.
(Sorry for that short off-topic)