I did few prototypes before to decide for this one. It is using 2 short prisoner nuts from MPJet (3mm). The front one will be glued in the fuselage and reinforced with some fiberglass. The rear on is inserted in the servo tray. The second 3D printed part is glued with cyano in the fuselage. Installing the servo tray will be pretty easy: Just slide and click the rear 3mm screw, then crew the from and read with a screwdriver. Servos will be maintained in the tray with a bit a rapid epoxy.
The STL file can be found here: