I noticed in the owners manual that on page 657 it states "Repeat steps 8-9 until GAIN setting is at a point just below trailer wheel lockup.If towing a heavier trailer,trailer wheel lockup may not be attainable even with the max GAIN setting of 10". Heavy Electric on the trailer brake page on the 8.4AN states above 10,000lbs.Possible with the trailer hook up,full fuel,trailer loaded with all the gear we use on our trips we could be over 10,000LBS.Certainly with the "Light Trailer" setting on the trailer page my trailer does not lock up,it slows it down real quick but not to the point of lock up.This is with the gain bar pulled completely together.I have never tried the "Heavy Trailer setting yet.Because with the Autobrake,and gain set at 6.5 the trailer brakes just fine.Also one thing I have noticed is that my AutoBrake setting it comes on as soon as I tap the brake,but as the truck slows down and I release the brake pedal, I some times never see the autobrake application again even when I am coming to a stop.Snoking nice view out the back,are you planning on painting a stripe on the back side of the receiver head to align with the pin.