Warden,
The parallel flow condensers may not look any different than a transmission oil cooler, although I have no experience with them, but my guess is that they have been R&D'd to be more effecient and meet the requirments of making 134 suitable to use.

it appears that the overall dynamic's of using 134 prompted the need for some changes in any 134a application, be it a desktop refrigerator or auto ac.

Leatherman....
great idea, on isolating R/D's with valves.(long as you can get some good valves that will not leak.

you would still need to evacuate the R/D canister & hoses since they are full of regular air. right?
if so then you'd need to throw a valve in per canister.

(my understanding is) The accumulator/orifice type system is less complex than expansion valve type, and I do believe it uses some type of desicant bag for isolating impurities, however, I've just got to believe, engineers would have stuck an accumulator type resivoir on the R/D system had it been feasible.

Look, if you really want your condenser coil to work effeciently, then forget about any high velocity electric fans.
What you do is reroute the condensing coil to a Coleman cooler in the trunk. Fill it with ice every day before you leave the house.

Now, if you are going to have your hoses "re-hosed"... would you use the "barrier" type hose?
I ask be cause maybe you may want to go to 134 someday, (you know if you get too cold while idling in traffic with R-12)
www.centuryautoair.com (Tucson, Az) quoted me around $40 per hose. I thought that was reasonable, however, 82 240 has 4 gas hoses plus the liquid line!

I am very interested in your "parallel" condenser upgrade with the R-12 application. This system will be so efficient You may not need an AUX fan at all!

How old is your R-4? still healthy?

Keep us posted.
dave.