I have no personal experience with the pareallel flow, but I have read several stories regarding their increased efficiency.

I think the cold air at idle problem was directed toward a system converted to 134. I think the parallel flow would help but we have no way of confirming until we have a guinea pig. It sounds like your willing to offer yourself and your 123 up as the guinea pig.

If you follow through with this, please let us know exactly which size condensor you used and your results.

I'm sure you're aware that you'll have to make two new hoses. This shouldn't be too big of a deal. I expect to get a hose crimper before too long. I am starting to collect some more equipment for a/c work with the idea of doing it professionally in mind.

I pick up my recovery/recycle machine today, then I will get a refrigerant identifier, sealant identifier, and then a 134 recovery machine. There is a hose crimper for about $200 that looks like it will work well with a vise.

Sorry to ramble. Please keep us posted on the project.

BTW, I agree that I don't think an extra receiver will do much, but it would be just one more place to ensure condensation. Remember having more refrigerant in the system won't gain anything, it's having more thermal capacity for condensation that will result in more cooling capacity.

Good luck,