Take a look:First, my apologies for replying to this thread after over a year, but I just saw this today.
I have an almost identical system - IQ4 back, Cambo DB-XL, Rodenstock 105 floating element macro. Your automated focus stacking setup looks terrific.
I'm curious about how you attached the servo to the fine focus adjustment on the rear standard. It looks like you have some kind of bracket attached to the rear standard and some kind of replacement for the knob? Were those custom machined or off the shelf parts?