I agree with you that R12 systems are superior in every way. I've owned only 1 new car ('96 Chevy Z-28). It came with an OEM R134 system that works well under most circumstances, but still would loose capacity and stop cooling when idling on a hot day.
The thing is the converted MB system seems to work well unless the sun is shining. I haven't had anybody check it out yet, but there is (hoping...) maybe just something wrong with the system and not just "the way it is".
The best A/C I've ever had in a car is an '88 Toyota Corolla with a nippondenso compressor and R12. I still have the car and it still has its original R12 charge with no service whatsoever.
Question: Is it LEGAL to convert back to R12. I guess the system originally came with R12, but I was under the impression that you couldn't refill a system with R12. Maybe I'm wrong. Of course one of the guys in the office has a license and can service all sorts of A/Cs, but I still would be concerned if it weren't legal.
What else, '73 MB 280 SEL (Lt Blue)
Daily driver: '84 190D 2.2 5 spd.