ok that small pot is the steering encoder and from the sounds of it it is working
the encoder(as you describe it) on the tiller is probably what yale calls a tach generator, they used those on thier orderpickers also.

inputs from both go into the lift amp? are you sure its a lift amp? and not a steering controller?

As for any supplements? no i do not have any, this model sounds like a new and improved version they designed themselves after the "schaeff" version that had at first when that model first came out.

I'll check around and see if i can come up with anything, or maybe someone else can jump in here and help? guys?