I would leave the walls alone and go through the floor. Here's what I did in our 5th wheel.
http://www.openroadsradio.net/forums...highlight=pass
There are no cables involved. It's just a weather proof tube through which I can run any type of cable I desire, coax, twin lead, power, battery, whatever. It never goes obsolete, and I never have the wrong kind of cable/wire.
The tools involved cost more than the materials. It was pretty cheap.