The AFS AHRS/magnetometer I installed said to keep it from certain things. The location you show seems to put it close to the battery (although it's a bit hard to tell where exactly you installed it). Here's an excerpt from the AFS manual:
Mounting Location (P/N: 72010 or P/N:8350-0480)
The remote magnetometer must not be located within 24 inches of any large, moving, ferrous metal objects such as landing gear components, motors, steel control cables or linkage. Avoid any metallic objects that may change position between ground operations and flight operations, such as landing gear, flap actuators, and control linkages.
The remote magnetometer should not be located close to high current DC power cables or 400 cycle AC power cables and their associated magnetic fields. Wires carrying high currents, alternate currents, or intermittent currents can cause magnetic variations that will affect the unit. Keep wires with these characteristics at least 24 inches away from the remote magnetometer. These wires can include:
Battery wires
Strobe wires
Autopilot control wires
Position light wires