I used a Tow-V-Aire for 6 years and it performed quite well. As I recall, I ran mine at about 38-40 psi on a 3300 lb toad.
If you feel the toad braking, i.e. it is pulling back on the coach, the pressure is too high. You do not want to use the toad brakes to help stop the coach - it should just be stopping itself. Once you feel the toad brake drag, back off the pressure until it stops and then back off some more just to make sure. If the toad brakes start helping stop the coach too, your toad's service brakes will wear out real soon.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL