I have made a 4th attempt after having found that 1) unfortunately I couldn't use Jeff's settings on my PJ (gamut completely off, especially red, so this confirms what Jason said about settings not necessarily working from one PJ to the other) and 2) my contrast setting was too low after the gamut calibration (I forgot to check afterwards).
So I came back to a 0 contrast setting, and readjusted greyscale and gamut (following the contrast adjustment, green had slided back well into the gamut, and some of the secondaries were off as well, particularly yellow and magenta). The numbers don't necessarily look better, but the picture does because of the contrast correction. dE for cyan is slightly worse (10) because of luminance but its position on x,y is better (almost spot on).
Here are my last settings (50 hours on the lamp):
Gain R=0, G=0, B=-64
Offset R=4, G=0, B=1
CMS Advanced settings (H S B)
Red -3 -19 3
Green -11 -3 30
Blue 18 24 -12
Yellow 3 -5 30
Cyan -3 -30 30
Magenta -3 0 0
A compilation of tips for those about to embark:
1) If you use HCFR and i1, don't start any measurement on a black screen, it freezes or takes ages to start. Start on any non black screen, and go to the first screen when it tells you to. It's mainly a problem when measuring greyscale (if you get to the 0 IRE screen before clicking the greyscale icon). It's not an issue for the gamut as it starts on a red (non black) screen.
1b) set the gamma reference in your unadjusted (or resetted) gamma preset before you start working on the greyscale.
2) Work hard on the high end/low end color temp adjustments (try to get it as close as possible over the whole scale, especially 10-30 IRE, before you move to gamma). The less gamma adjustments you have to make, the happier you'll be. Also copy your gamma settings before any change, as a minor change at one point can throw the whole scale away.
3) Before adjusting gamma, have a look at the biggest bumps and try to get these better instead of going in sequence (10, 20, 30). Look at the greyscale after any change and go back if it gets worse (it will!).
4) When working on the primaries/secondaries, concentrate on green first, as it's (with yellow and cyan) the color that's the most over saturated. Or depending on yor priorities, you can concentrate on cyan, but I never managed to get it completely right so I compromised on this one.
5) First try to find the right setting for color. I did this by setting the brightness for green to 30 (you'll need it anyway), and then try to find the color setting as close as posible to 0 that will bring green within the gamut, then use saturation to push it back. Jeff and l found -8, Jason apparently betwen -22 and -15.
6) For the colors that don't need full brightness to compensate for the lower color setting, find the right setting for brightness (or get closer) before you work on saturation, as they for some reason affect each other. On my settings (-8 for color), I am short on brigthness for green, yellow and cyan, so I know I'll need 30 brightness anyway, so I set it to the max and then work on saturation and hue.
Sorry if these tips are obvious to most of you, but I thought it may help rookies like me to save a bit of time!