I contacted him a number of years ago about his R-12 replacement for my old 1975 Ferrari, rather than converting it. It worked perfectly - better than Freon-12, even. Which is the only reason the EPA refused to allow it to be widely used. His web site (ghgcool, IIRC, I'm sure long gone by now) taught me that you can also mix butane and isopropane as a superior drop-in substitute for R-12, but he didn't pursue that approach because he knew that the EPA would kill it on safety grounds - even though it was only slightly more flammable than R-12 with the required compressor oil mixed into it.

George was a really interesting guy, a true hacker's hacker, and I truly enjoyed talking with him.