Re: First and foremost, lets stay cool - Air Condition
You should be able to read the temps on the fittings, no?
I think you could use automotive lines and/or steel lines, or better grade copper. The right answer probably depends on the distance between the units.
Biggest problem I see is where to mount the "outdoor" unit. They seem to need premium space. My initial guess is right behind the driver above the wheel well boxed in for a bulkhead mounted indoor unit. Rear wheel well for a rear unit, part of a mechanical room. They are too big to hang on the rear bumper and still use the rear door or mount below deck.
I wish they made inverter style window units.