Here's a photo showing how I installed the shelf for the Pinpoint Magnetic Sensing Unit (MSU) in the tail of my Legacy:

 

 

I hot-melt glued the wood blocks to the sides of the fuselage, protecting the fuselage with clear packing tape first.  (Without the clear tape, the hot-melt glue is a pain to remove from the carbon.)  The shelf is a piece of left-over carbon, probably from the lower cowl cutout for the nose gear wheel well, I don't remember.  Before installing the shelf, I cut the hole in it for the MSU and drilled the three holes for attaching it.  I set the shelf in place, leveled it front-to-back and side-to-side using the long bolts, and then did carbon BIDs to bond the shelf to the fuselage sides.  Once the epoxy cured, I removed the wood jigs and the clear tape.  The MSU is so light that even at maximum G there's not much force applied to the shelf, and this seems to be strong enough. 

 

I put the shelf as far back as I could reach, which turned out to be about half way between the aft baggage bulkhead and the rudder bellcrank.  I put it as high as it would go and still have plenty of room to drop the MSU down through the top of the shelf.  It works; my MSU compass swing had relatively small errors and I get no heading change when I move the rudder pedals or use the autopilot.

 

Dennis Johnson

Legacy, now flying