When I set up my brake controller I had neutral braking; not too much trailer not too much truck. On all our travels I have been satisfied with the braking even when braking hard. However I never was ...
If you can't lock them up using the controller you may want to check the adjustment of the brakes on the trailer, I don't trust the self adjusters that are there.
I did find my self in a hard stop a few weeks back and I locked them up and yes a whole lot of pavement goes by in a hurry.