We just installed the drain pan, Splendide, by drilling a small exit hole (1 1/4") next to the dryer vent using plastic tubing. We installed the dryer vent near the front of the cabinet and removed the drawer. To cover the hole, I found a stainless steel claim shell style cover at a marine store. To hold the plastic pipe in place I ran a small screw through the tube into the wood framing of the trailer just behind the fiberglass skin. I then trimmed the excess tubing flush with the outside of the trailer. Then I used silicone caulk to fill around the hole and seal it.
The other option was to try to run it with the supply lines and drain pipe that run under the dresser and exit out near the landing leg. We had tried to fish the plastic tube through to no avail. Not wanting to drill into the box housing the supply lines, the only other way we could think of was to remove the dresser and try to disassemble the box. That is why we went to plan B using the claim shell cover.