My tow dolly has surge brakes built in.
They have worked well.
In using them I was reminded of what was seen
when towing boats.
Some things to remember...
Towing down hill will put pressure on the surge activator.
This will in turn activate the brakes to some degree.
Same in stop and go traffic.
This can cause them to over heat. So keep a watch
and let them cool as needed.
Also a soft start after a stop (creeping away)sometimes
causes the activator not to fully disengage.
A quicker start will make sure the activator disengages.
A search on boat trailer's with surge brakes, brought all
these items back into my memory as they are common with
surge brakes.