I've been running the Sumo Springs for a few years now and I really like them. They do not engage when light loaded and when I load the TC, they do exactly what I need them to do ... provide extra suspension support and cut down on sway. No maintenance was also a big attraction for me. I'm very happy with the Sumo Springs. I got the 2,800 lb. variety. If you search my posts, there is a full write-up.
2007 Adventurer 90fws Truck Camper
2001 FORD F250 SuperCab; 8' box; 4x4, 7.3l diesel, rear Sumo Springs