Hi Mark,
I'm still waiting for my new P25 for my H1, but at the moment I'm using the H25 on my RZ. I recently shot a fashion job on it, which included some really tricky fabrics and I had some moire problems, too. I agree with Damian that the Phase One Demoirize filter in PS is a good way to go when you have colour noise, but it still doesn't quite cope when you also have the density banding that goes along with it. The monochrome textile option is pretty crap, so I opted for the advanced option and fiddled a lot with the size slider to find the optimum result. What I found when going back to the files is that those images that were even slightly out of absolute focus were the least problematic in terms of Moire. I know this is stating the obvious and that it isn't really practical to shoot out of focus, but if you are shooting tethered and can preview your sharpness, you may be able to slightly defocus when needed and re-sharpen later. I found that putting the chip on an angle did very little other than make the moire change direction! Blue and camel colours seemed to be the worst offenders.
Ultimately, though, when the images were viewed at their final print size, the slight moire was a small price to pay for the incredible detail the Phase backs can produce. My client was extremely pleased and the pre-press guys said they had never seen fashion shot digitally that well before!
If anyone finds better ways of reducing moire (and not the blur>average>fade average>hue etc thing which I've tried before and find not as good as demoirize), I'd love to hear about it as it seems to me to be the only stumbling block for my work at the moment.
Good luck Mark and hope I will be sharing more P25 experiences with you all soon. (I think Santa's sack may be empty though, I'm afraid.)
Regards,
Lucas
www.lucasallen.com.au