I have three magnetic mount antennas on the roof of my Dodge RAM.
On my truck, the factory installed Satellite Radion antenna is centered left-to-right and mounted maybe 2"-3" from the rear edge of the roof.
Even (front-to-back) with the Satellite Radio antenna and maybe 2" to the left, I have mounted a Wilson Electronics Cellular Antenna. then maybe 2" to the right of the Satellite Antenna, I have mounted a Wi-Fi Antenna.
Finally, behind the Satellite Radio antenna, I have the Garmin 18 hockey-puck style GPS Receiver/Antenna mounted.
Because of this tight pattern of 3 antennas around the factory mounted Satellite Radio antenna, I was able to route the 3 thin coax cables from the antennas straight back to the edge of the roof to the high-mount break light/cargo light assembly.
I remove the lens (2 screws - Phillips head), then with a razor knife, I carefully removed 3 strips of rubber gasket material in direct line with the 3 coax cables. The 3 strips removed were about 1/8" in width.
I routed the ends of the 3 coax cables into the roof through the hole where the light assembly was, fished them out of the headliner at the top of the rea window glass.
I filled those 3 strips cut in the lens gasket with clear silicone rubber (RTV), then I carefully set the lens back into its mounting spot and pressed the coax cables into their respective slots. Replaced the 2 screws, then dabbed a small amount of RTV on top of the coax cables at the 3 entry points.
Many months of rains later, no leaks!
For interior routing, I merely tucked the cables into the headliner all the way over to the drivers's side corner, then behind the plastic pillar and out behind and under the back seat. The WiFi and Cellular cables end under the seat for use at the Router and AirCard. The GPS antenna plugs into a USB extension cable, then under the door entry moldings/carpet and under the driver's seat and plugs into the CarPC.
I can take pictures of any of this if they will help you. Until then, below is one image. Also poke around here -> http://www.beletti.com/
. Click on CarPC from the menu.
Best of luck,