Actually carmatic (and I shouldn't be answering this because it would be better suited in the radio or car forums) the D/R on a aircraft radio is a switch that has preset amounts of deflection either high or low (preset by the pilot), the D/R on your surface radio is only on the steering and is more of an on the fly EPA in the fact that it allows you to add or subtract directly from the preset epa with a multi position thumb wheel.
in an aircraft radio there is no adjusting the amount of deflection of the D/R while flying it is either in the preset high deflection or low deflection position. and you only need to change the EPA on the steering to give it max throw without binding the linkages.

Sorry Kevin I didn't mean to jam up your post like that but most car guys have no Idea as to the function of there radios except forward real fast, and turn. Congrats on your first flights and I am glad to hear the Senior came home in one piece. I too trained and soloed on a Senior and it is a joy to fly. and is also alot of fun to shoot touch and goes with. Good luck and hope to hear that you soloed soon.