I created this GPS cover for my APM 2.6 from DealExtreme, used on the great crossfire 2 3D printed cuadcopter. Drilled four 3.5mm holes on the top cover and used four m3 nylon screws and eight M3 nylon nuts for perfect and solid fix.
Printed with PLA at 10% infill without supports. I mounted on picture position and configured with Mission Planner COMPASS_ORIENT=6 (Yaw270).
This GPS-Compass module is branded as ZnDiy-BRY and measure 50x50mm with four munthing holes at 5mm from edges (45x45mm square).