RE: Servo screws
The best way I have found to keep cowl (or canopy) screws from coming out is to enlarge the hole in the block to 1/8" and glue a piece of nyrod tubing into it. make the tubing a little longer than the block to be sure it is fully glued in place. You'll need to tap it in with a hammer. Then enlarge the hole to 5/64".
Now a #2 screw (standard servo size) will screw into the nyrod and will never vibrate loose!