Worked on right wing inspection plate "C". Removed one of the four previously installed nutplates to accomodate the need to position the magnetometer to a cardinal direction. Chose east...so drilled out the nutplate already in that position which interferes mechanically. Significant amount of time measuring and positioning the device, and got it drilled and installed. Garmin spec calls for it to be within .5 degrees (that's 1/2 a degree) so it matters. Then basically repaired the plate itself for mounting a 4th screw in a different clock position. So magnetometer is now aligned at 3:00 and the plate screws are at 12, 3:20, 6, and 9.