Stainless steel pins are used for the locking mechanisms. They were machined with grooves for 4 C-clips but I have listed external push rings which will work although you will only be able to install 3. Be sure to round off at least the one end of the pin so it will slide easily into the locking hole. Stick a block under the outer locking ring plate of sufficient height for the locking pins to clear the next ring by about an 1/8" and slide the inner locking ring up against the wall and seat in place with the external push rings. We reamed the locking pin holes to 0.128" and got a nice sliding fit which would stay back out of the way when in free swinging mode.
We used slip rings from Adafruit (https://www.adafruit.com/product/1195) to get power and data into the center.