I think what Andy is referring to is a new Carrier Air V installation on a vintage AS.
The Carrier Air V needs to be modified by removing the external shroud and then removing the internal cover that covers the "Slinger Wheel". After you remove the cover you have to drill a hole at the LOWEST point in the "Slinger Wheel" drip pan. The hole has to go all the way to the inside of the trailer. That means you have to drill through the plastic "Slinger Wheel" drip pan and through the metal underneath the drip pan.
Once you make the hole you have to get a fitting a little smaller than the hole that has O.D. threads on one end and a hose barb connection on the other end.
I also used two O-rings that fit snuggly over the threads of the fitting. One on the inside of the trailer and one on the outside, in the drip pan.
You can pick up a fitting like the one I am talking about at nearly any hardware store. I got mine from a local Ace Hardware. They are plastic and it came with a plastic nut for the threaded portion.
I siliconed, (oh no, the dreaded "s" word here), the fitting into the plastic drip pan and in the bottom inside the trailer.
After all that, I hooked up the drain tube from the trailer to the barbed side of the fitting and used a standard hose clamp to secure it.
This works like a charm. No runs, no drips, no errors!