No problem with routing the longer hose that Retroair/Classic Auto Air provided as part of their upgrade kit

On both cars I've used the upgraded Retroair/Classic Air evaporator and more powerful evaporator fan.

Added a trinary switchs since converted to R134a

On my current car I used a Griffith front condenser. (Remember to place a fuse in the front blower harness!)

I've recently converted to a hydrocarbon refrigerant because it is cheaper and I can do it myself but unfortunately haven't any data on changed performance over 134a.

Retro Air does not answer the phone and website not helpful

Because Rock sold Retroair to Classic Auto Air a few years ago.

Try here:
https://www.classicautoair.com/porsche_air_conditioning_porsche_ac/

They are the ones I called. Retro Air rolls over to them. Never picked up. Have you worked with them recently? Do they sell individual parts?

I found Rock good but subsequently found Classic Auto Air not as good.

If you want the best in terms of quality and service, plus they sell individual parts, just go to Griffith:

https://griffiths.com/

This. Griff will answer any AC question, and only sells good equipment. Either a single switch, or the turnkey full system. He does golf a lot, so sometime you have to wait for a call back. And his instructions are the best.