Tell us about yourself!
I saw your update, April 27, 2017, but haven't found the new stl files. Are they available? And your code for the extra servo board and servos? I recently got a NVIDIA Jetson Nano and want to try stereoscopic imagery. Maybe I can get the plastics printed before the cameras arrive...
Build a Giant 3D Printed Robot Arm
PCB Concepts and Materials
Circuit Board Design Class
Nice project! Suggestion, if you're using a 4 x 4 electrical box then you can bring your mains power in once and use it internally for powering your circuit and connect power receptacles through the relays, one per relay. If you squeeze hard enough you could power four sockets with one esp8266 circuit. The headers take a lot of space and can lead to poor connections over time. I get boards without headers attached and solder directly to them. 2x relay bd. $1.22, ESP8266-01 $1.99 for example.