I spent a lot of time pondering the stab servos, I didn't really want the head of the servo sticking out, so that forced me into a horizontal installation.

So, I basically installed a false rib made of 3/32 aircraft ply into the stab where the servo would mount. This took a bit of figuring with one stab to get the shape, servo cutout etc. just right before I made the rest of the ribs.

In order to have a nice surface for covering you want the rib to be just slightly smaller than the surface of the stab skin so that you have filler there to sand. But not so small that you dont glue to the skin, so with only a 1/16" skin you don't have much room.

So first cut the slot in the stab through on both sides, be accurate. Then use a dremel with a router attachment and a long zip style bit to bore out the slot from the root rib so you have access to the servo. Only remove as much material as is required to get the servo in and out, so that your root rib has as much bonding area as possible.

Once thats all done up, glue in the root rib carefully with polyurethane. Sand the excess down when its cured.