The EZ Pilot control unit is a square box with the dimensions shown above. The 2.75" depth includes the 25 pin connector at the rear of the unit. You should allow an additional 2-3 inches behind the control head for the cable connector and backshell that will plug into the unit.
Although the control head is square, it is designed to fit a standard 3-1/8 inch instrument cutout. It is positioned at the rear of the panel and held in place by 4 ea #6-32 screws.
The servo assembly is placed where there is easy access to the aileron control torque tube. The servo dimensions should be carefully considered before selecting a mounting location.
Click here for servo dimensional drawings