Hi Eric, Sorry for the 6 month delay in response, I just found your comment tonight! I'm not sure I remember a great deal about the manual proportioning valves, as that was about 7-8 years ago! I sold the coach almost 5 years ago. They were installed by Tiffin(under warranty) at the Service Center, so the 'placement' was determined by Tiffin. Later a friend and I relocated the valves to a rear PS bay, so that the valves could be adjusted more easily. My target was a 75/25 drive/tag axle proportion, which translated to a weight of about 6500# on the tag axle. Less than that and the tag would skid on braking. The dead weight of the tag axle was about 3000#. Hope that confirms what you have probably already figured out! If other questions, pet me know. Kent