The second ServoCenter card arrived today. This one will be installed in R2-D2's dome and control all of the servos via computer control. The card will communicate with the first card via a slip ring wiring connection. This, like your steering wheel, allows for an electrical connection thru a rotating linkage.
I'll have to solder external power connections for the card and the servo power source, just like I did the first card. The cards communicate with each other via a serial (DB9) connector. Only 3 wires (pins) are used to establish a TTL data communication between the cards. I can route those three wires thru the slip ring. I can daisy chain many of these cards but two should be fine.
Like everything else with R2-D2, the challenge will be mounting the card inside the dome and the wiring fun.