I'm not up to snuff about this new conversion, but, like you, I was doing R-12 to R-134a conversions way back. I was privvy to an automotive A/C engineer and he taught me that the condenser of a 134a needs more surface area than R-12. He showed me a condenser made at that time by some independent dude/small business, that went to "parallel/series in function, and to use PAG46 across the board. Every time I replaced the original condenser with this dual design function unit and replaced the oil, the A/C worked well.
I DO know, from going to a class, where the instructor handed out 3 inch cutouts from both a R-134a condenser tube, and from a 1234yf condenser. The passages of the yf1234 condenser are so tiny, that I wonder why the oil doesn't clog up the works. The instructor said that the days of adding oil directly to the condensers of the yf1234 are over, because that can stop them up! They CANNOT be flushed either.
