[carnut]

Found this page interesting. It has detailed photos of a secondary compressor installation. Nice to see what it would like.
http://proairllc.com/image/data/docs/Promaster/09%20000%20420%20Install%20Instr%20DPM%20Comp.pdf

 

[Chance]

Seems there would be an even greater demand for a secondary alternator. This looks a little different than what I've seen, but it's good to know of this option.

PMs should have a factory option like Sprinters for a bracket for either A/C compressor or alternator. Even better would be a second alternator option. It's so much cheaper that way that it becomes a no brainer.