Trailer Brake Stopping Distance

I am going thru this very thing right now too. Just had the trailer brakes checked and adjusted at a dealer. I have a '14 Silverado and the controller is up to 10 also and it wont lock'em up either. Taking the truck in to the chevy dealer to have the output checked on the integrated controller. Here is what the trailer dealer told me...... The integrated controlers are PROPORTIONAL, my old Tenkosha primus was an INERTIAL and they operate differently..... okay......so why can I still not lock'em up with the manual switch on the dash?? shouldn't 100% do it? I'm getting ready to go out west and will be in REAL mountains so I need to know the brakes are working properly. Why is that so difficult??