Some time ago, I wanted to play around with alternative RGB profiles. I found quite a few on the web, but narrowed it down to DonRGB, Max RGB, and Best RGB for the time being. These go deeper in the green than Pro Photo and have no imaginary primaries. They can be downloaded from the hutchcolor site.
I added Best RGB, Don RGB, and Max RGB to Library/Apllication Support/Adobe/Color/Profiles and now they appear in the list of profiles I can convert to in PSCS5.1. I used Open Image and converted the raw that was in Pro Photo 16 bit but had not been edited at all, to Best RGB 16 bit and saw no visible difference but there were no deep greens in the image.
I had opened the raw in ACR 6.7 as Pro Photo 16 bit and then clicked on the profile name in the bottom menu bar to show the Workflow Options where you can set the opening profile. The pull down for profiles still shows only Adobe 98, Pro Photo, Color Match, and sRGB. Where is the App Support folder for this list? I had already looked in the most likely places in /Adobe. I haven't added the new RGBs to ColorSync as yet. One thing at a time.
Mac OS 10.9.2.