The main problem with trailer brake controllers on DPers , is that some ; like mine ; activate the brake lights when the exhaust brake is operating, and with the wrong controller, long downhills using the exhaust brake, could over heat the trailer brakes.
I believe that , Tekonsha , with true proportional braking doesn't have that issue.
There are a few threads here in the forums about the issue.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.