Rear servo mount is built using vertical rails in aft fuselage side cavity.
Mount the servos and double check clearances. Shim with scrap ply to space servos outward.
When installing side stringers, anchor the stringers at edges, cut excess to clear servo cavities.
Then build up around servos with 1/4sq balsa. Sand/taper everything to fuselage contour.
Idea is for covering to look smooth over this area, even though there are rectangular holes in there.
Both sides are identical. Lower cavity (rudder servo) will just be left covered up on one side.

Landing gear fairing is just a hollow balsa box I improvised in place. Weighs next to nothing.
Mounts using two #4 capscrews into spanwise rails over the main gear.
Look closely at my earlier cowl bottom picture to see how it fits together.

Hope this gives you some good ideas. Post pictures of your creation when done, OK?