When I was building the mount for the magnetometer, I forgot that the outer strake bulkhead is not parallel to the centerline of the fuselage. The documentation for the magnetometer says that is can be calibrated for up to 127 degrees, but it was fairly simple to ream out the mounting holes to allow for that.

Here’s the modified bracket which compensates for the alignment.

To get the front-to-rear and side-to-side level, I put in the bracket with just the bottom plate. I used a level to determine how far out it was. Then it was just a matter of adding a washer or two and a little sanding to remove some material.

The finished mount with both magnetometers installed and ready for cabling.