Garmin GMU 11 mounting

All,

I am coming up on mounting the Garmin GMU 11 magnetometer. The instructions say to mount within 3 degrees of level flight. Any idea how to determine that? Wings are off right now. I know this is some combination of dihedral and AOA of the plane itself in level flight. I am trying to translate that into an angle relative to the ribs on the underside of the wing, if that makes sense. I was planning to bolt it to a small balsa plate hysoled to the ribs, or between a rib and false rib. I guess I could try to make in adjustable, or put a shim in later through an inspection hole if I needed to, but would like to get it close out of the box.

Thanks

Scott

For building purposes, flight level is considered to be when the front and rear spar carrythru tubes are level, or when the bottom frame tubes under the seat are level. That's what the build manual calls flight level. So if the wings are off the plane, level the spars at the ROOT END, not further outboard because the built-in washout will change as you go outboard. If you are mounting the magnetometer out near the wingtip, it would be more accurate to have the wings on the plane and rigged properly, because an unmounted wing will sag some and not retain the washout accurately. All of this is probably within the 3 degrees allowed, but if it were me I would level the fuse with wings attached.

I got an app with a digital level. Mounted the wing and then just took the angle the fuselage was at and then out of birch built a platform and matched the angle of the platform to the fuselage. I saw no reason to level the fuselage other than left to right.