I just completed my Pixhawk equipped 4WD Slash chassis complete with dual GPSs and a 3DR 915MHZ telemetry radio.
The GPSs are mounted at each end of the chassis. The 3DR GPS/Compass module is in the front of the chassis and 3DR uBlox LEA-6 v1.1 is in the rear. Both are protected by the chassis bumpers
The rest of the components are mounted on a navigation platform above the battery.
The rover is powered by a Traxxas 3500 brushless motor and VXL-3s ESC and is using a Spektrum Remote Receiver to communicate with a Spektrum DX8 Transmitter.
I have beefed up the body mounts with extruded aluminum "L" rails to help prevent damage during a rollover.
Unlike my 2WD Slash rover, the battery can be removed for charging without taking the navigation platform off of the chassis.
Here are some pictures of the new rover:
TCIII ArduRover2 Developer