Well we bought an Everstar 9500 Portable AC at Home Depot for $299 so I wanted to let you guys know how it worked out in our Viking SP230. So here are some Pics and comments about how I did it. The AC unit has a 5 inch exhaust hose but I couldn't find anything that was 5 inch to use to go through the side of the Camper. Finally I found this 4 inch "Dryer Dock" and this 5 to 4 inch reducer. I figured I was only restricting it down to 4 inch at the very end of the hose for a few inches so it probably wouldn't hurt. The Home Depot part number for the Dryer Dock is 610589164101 and the Home Depot part number for the reducer is 050206925607. I thought about only using 1/2 of the Dryer Dock so it would be flush mounted to the outside of the Camper but the plug I bought to use when traveling or when the AC is not in use was going to be very tight. We took a look and figured right in front of the sink was the best place for us to locate the AC unit since we had room under the cabinet to route the exhaust and exit the Camper. I started by marking the hole on the inside and cutting through the inside paneling with a small hole using my dremel tool. Then I poked around in there making sure that there wasn't anything behind there where I was going to cut out. I used the 5 inch end of the reducer to mark the inside hole since it would end up being recessed in this hole. Once the inside hole through the paneling was cut out I then used the 4 inch end of the reducer to mark where the 4 inch was going to come through the outside of the Camper and cut it out with my dremel tool. This top picture is where I had enough room to get a screw in each side of the reducer to hold it together with the Dryer Dock, this is because the 5 inch end of the reducer won't pass through the 4 inch outside hole. The second picture is a view inside the hose and the third picture is a view of the outside finished. The first picture here is how the exhaust hose is left stored and the next two pictures show the AC unit sitting in place connected to the exhaust hose. I found this 4 inch pluming test plug to seal the hole when the AC is not in use or when you are traveling. The Home Depot part number for the test plug is 038753334035. In the last picture the plug wasn't seated all of the way in the hole but can easily be pressed in all of the way. I didn't have time to put the finishing touch on that test plug but I bought some white Rustoleum spray paint for plastic that I plan to use on it to make it blend in better.