My last camper did not have outdoors either. I got the wiring on the back of the radio figured out and in my situation it was easy to run the wires to an outside storage door and left enough wire to have a couple feet of slack. I mounted two threeway Infinity Kappa Series speakers I had in plastic coffee ground containers. I cut a hole in the bottom of the container and screwed the speakers to it. I hard wired jumper wires to the speakers with a bit of wire and sodered connectors to connect the the camper wiring. I mounted the two speaker units together with a 2x4 that was 4" long and 2" wide and the front and 1" wide at the back so it looked like a wedge and screwed each speaker to it so they projected at different angles when mounted. Finally I ran a 4" carrage bolt threw the 2x4 and ran a nylon nut on the end of it leaving some thread exposed. The thread of the nut match an exposed bolt on the bottom of my camper. So in short I would mount my homemade speakers to the underside of my camper during set up and take them down when in transit and did no cutting or extensive wire running though the unit to get outdoor speakers. Pics tomorrow... sounds cobbled but it worked and took 30sec to hide in storage to prevent theft and had most everything in my garage.
