I have towed my camper since 2005 with a 2004 2500 Silverado and a 2004 2500 Suburban. Both of my 2004s have an aftermarket brake controller. I have always set my brake controller gain so that if I squeeze the brake controller while on gravel it will lock up the trailer brakes and if I squeeze it on pavement it won't quite lock up the trailer brakes. To set it that way the gain is around th emiddle of the range on the brake controller. I towed my camper with my buddies 21 3500 Silverado. With the Chevy brake controller gain maxed out at 10, it would not lock up the trailer brakes on gravel. So I tried it with my company truck (22 2500 HD) and same thing. With the gain set at 10 it would not lock up the brakes. I just bought a 24 2500HD. Same exact thing. I just had the camper inspected and told the mechanic about it. He said he adjusted the brakes out till they were touching the drums and then barely backed the adjuster off. He drove it and agreed the brakes felt weak but couldn't explain why. I hook up to my 2004 Suburban with the after market controller and I can still lock up the brakes with the gain at mid range. I believe the Chevy controller just can't supply enough current as the old aftermarket controllers.
