I was reading last February's Trailer Life and noticed this article. You may have been aware of this already but it is still something to keep in mind.
Safe journeys.
Inertia-Activated/Proportional Braking Systems
Proportional controls are popular for heavier trailers because they deliver smooth braking and are able to detect the difference between gradual deceleration, like slowing for traffic, and maximum stopping power required when emergency braking. However with either pendulum or accelerometer units, if the tow vehicle can't get enough traction to slow down sufficiently to fully activate the controller, the trailer brakes won't be applied sufficiently. This might happen on ice, snow, wet leaves or sand, or if the tow vehicle's brakes fail in which case the manual override should be employed.
EXAMPLES: BrakeSmart; Draw-Tite Intella-Stop Ultra; Hayes G2; Genesis, Endeavor, Energize III and Energize XPC; Hensley TruControl Gold and Silver; Tekonsha P3, Primus and Prodigy; Silver Odyssey.
This could be a good thing to keep trailer brakes from locking up in slippery conditions or an unwelcome surprise if other conditions occur.