In the 2015 Vista I own which is now the Vista LX, I used a 1" hole saw to just cut thru the top fiberglass and plywood centered on the location hole. Be sure to use light pressure and stop immediately when you stop feeling the resistance of cutting plywood, you don't want to penetrate too deep and damage the wires or worse yet penetrate the inside ceiling. Then you lift out the layers and remove some foam directly below them to expose 2 coax and a 12 volt power connector. One coax goes to the main sat TV receiver location, other coax goes to the bedroom sat TV receiver location.
You are not drilling into a main wiring channel area, you are exposing a wiring channel that tees off a main channel so all you will expose and see is the coax and the 12 volt wire.