The same magnetometer is used in the G900X system. Most (all?) of the side-by-side RVs with that setup put it in one of the two forward lightening holes in the F-714 aft deck, i.e. under the empennage fairing.

mcb
 
The same magnetometer is used in the G900X system. Most (all?) of the side-by-side RVs with that setup put it in one of the two forward lightening holes in the F-714 aft deck, i.e. under the empennage fairing.

mcb

Matt, I would have assumed that was too close to the elevator bellcrank/weldment and the steel fasteners for the horizontal stab. If it has proven to be a good location, do you know if the same spot woudl work in an RV-8?

My previous magnetometer was mounted on a shelf on the top longerons, but very difficult to install and/or service.

Alternatively, is there a location in the 7/8 wing which is known to be good? The steel water pipe counterweights in the ailerons seem like they might be a problem outboard....
 
For the SP2 I just put in the RV10, I prowled the whole airframe with a hiking compass. The sweet spot was actually about midway between baggage & tailfeathers and higher had less deflection than lower. Try a compass check before you make a mount point. It may save grief (or not).