Well since my SDL is driving me crazy now, I'm going to finish on the SD's system here. Anyway, since that system is 100% dead I'm going to go through it all here. Which brings up some observations/questions...
A parallel flow condensor seems to be a pretty inexpensive upgrade for these vehicles. Maybe $120 for the unit and hoses, wouldn't this help
even on an R12 system? More capacity and efficiency... Now are there only universal condensors there or is there a place that sells direct fit units?
Who has one of these in their W126 with R12? How did it help sitting at idle?
Also, for the W126s at least we can use the late ~'90+ dual front aux fans to help keep high side pressure down and push more air. Shouldn't be too spendy once you find them. For the W116/123s you'll probably want to upgrade to a larger aux fan.
Here's a few threads I have found...
http://www.peachparts.com/shopforum/showthread.php?threadid=81979&highlight=parallel+flow+condensor
http://www.peachparts.com/shopforum/showthread.php?t=99598&highlight=parallel+flow+condensor