All I can say is that this sounds like a bunch of B.S. to me.
If you cannot lock up your brakes with the controller all the way up, you either have brakes that are too small for the weight of the trailer, or you have some form of brake or controller problem, end of discussion in my mind. That is different from having the brakes lock up in normal operation, they shouldn't, but rather be right on the edge of lockup where maximum braking occurs (ie. threshold braking) at approx. half controller gain. The temps might vary a little from axle to axle, but should otherwise be pretty consistent.
Anyway, that's my standard and I'ver certainly worked on some trailers to get there, but it is possible.
Let us know if we can help.
That was one of my main complaints to begin with, i could not adjust the brakes per common knowledge or manual because they will get no where near lockup at 13v. They help to slow the trailer a littel, but a majority of the braking is on the truck and i don't want to cook the brakes on a brand new truck.
From what i have found the axles are close to max, the trailer is 9600 gross, dry 6900 lb and has two 4400 lb axles. so 8800+ the 850 thats unloaded as tongue weight gets a total of 9650, reserve capacity of just 50lb. I have heard that the lippert 4400 are just beefed up 3500's, so maybe the brakes are undersized. If that's the case then i'm disappointed in heartland and my only option then i guess would be to put a set of 5k's under it or put together a disk setup.