Glad it helped, your greyscale indeed looks much better.
That dip in gamma is not too bad but - assuming you are in a light controlled room with a gamma target of 2.4 - you'll lose some dimensionality leaving it that way.
I would keep/save these decent results and in a different memory, try the following:
- use a 2.4 gamma preset instead of 2.5
- set the gains to D65 at 100% white
- don't touch the offsets
- using the gamma RGB controls, adjust your greyscale making sure that you adjust each color in the right direction regarding gamma. For example, if in the part of the curve you are adjusting gamma is too low (say 2.2 instead of your target of 2.4) make sure you lower the RGB controls as you adjust your greyscale, to make sure your greyscale adjustments move gamma in the right direction (up in this example).
- once the greyscale is ok, use the gamma white control (starting with high and going down) to try to flatten your gamma curve to your target. Then rinse and repeat with hopefully smaller adjustments.
- you'll have to find the right compromise between the three bands, but you should be able to reach a flatter curve than you have right now.
- if this fails, you could also try the different gamma presets and color temp presets to see if you can find a better candidate once you have set the gains to D65 at 100% (i.e. a flatter curve to start with).
If you want to take this further, one of you should probably start a JVC calibration thread for the current models because otherwise this tends to be OT for users who don't really care about calibration (lucky them, sometimes I wish I could turn the clock back!).
By the way, to leave your specifics and briefly discuss the generic (I know you personally already know what follows), I agree that these units offer a very decent performance OOTB with the right settings, but in my opinion this is just to allow the user to enjoy the projector as you break in the lamp and make sure all is working fine before calibrating. They really benefit from a professional level calibration at 200 hours and then a touch up at least every 500-1000 hours as the bulb/panels age.
This is true for most projectors. If you don't calibrate, the JVCs with the right settings are better than most to start with, but like all projectors they drift as their bulb/panels age. Some of this - normal - ageing effect can't be solved by simply replacing the bulb after x hours, as some of the drift, especially re gamma, is due to the panels. Without an autocalibration like what Sony offers on the 500/600ES, there is no way around that.
It won't make a night and day difference (at least until the bulb/panels reach 1000 hours) but you'll get the last 10-20% of performance you're missing without a good calibration. After 1000 hours the bulb/panels have drifted so much that a good calibration would probably transform the picture of a PJ left uncalibrated. Also the greyscale changes significantly when you switch between normal/high lamp or change the iris settings, so that's another reason to recalibrate as the bulb gets dimmer and you change these settings to compensate.
This will be especially visible in the greyscale/gamma calibration, as the gamut is very decent to start wise and while it can be improved, especially using a good 3D LUT calibration with an external processor like a Radiance, that's not IMHO where most of the improvements lie regarding picture quality (which every one should care about) vs picture accuracy (which only some, including myself, obsess about
Greyscale/gamma calibration make a real difference regarding how flat/dimensional the 2D picture looks. Simply adjusting white to D65 in 3D also makes a big difference for skin tones in 3D. To me these are the two things to absolutely do on these projectors, especially in a light controlled room, and even more in a bat cave.
Back to your specifics: