who makes those neat little servo mounting boxes?

The best ones are made by you. The plastic ones add a bunch of weight and you still have to build the rails and such to screw it to. Keep it simple and put in a good set of rails and be done with it. I usually use 1/8" lite ply to make the tray then either use bars of 1/8" aircraft ply below for the screws to bite into, or 1/4" bass wood. Both work well. The same thing goes for the plastic servo trays.

Don

Campgems has hit the head right on the nail. The plastic servo boxes you mention add extra weight to the plane, as well as take up room in the plane. I've found that it's much easier to just build servo mounts when they are needed, and built to suit the application.

Ken