Interesting, I remember going to some similar threads about R134 conversions but couldn't remember where exactly.
procaddytech, thank you for the very useful formula!
500hpgtx sounds good but we are in Europe and getting the AutoZone here would be pretty difficult
LMP, I will check what you said about the R143a. Btw, do you currently use the R134 or another alternative refrigerant in your A/C system?