Yeah, I would say if the Timbrens are not compressed against the axle under load, you will have problems. The factory suspension will give pretty easy, then the Timbrens will engage causing a pretty severe bump I would imagine. However, if the Timbrens are in constant contact with the axle under load, and even a bit compressed, I would think they would work better that way. The Timbrens are not a "progressive" system (like the RAS) where their action increases as the load increases. The Timbrens are either on or off, and if you're in between somewhere, I would think it would be a pretty rough ride.
After all that, I'm in your boat, I'm bumping up against the upper limits of my payload, so 3/4 ton truck is in the plans... Good luck, and happy hunting!
2014 Jay Flight 28 BHBE
2015 RAM 2500 6.4L HEMI, Tradesman 4x4, 3.73
Blue Ox SwayPro (BXW 1503)
Upgraded from an REI internal frame backpack and a Eureka 1/2 dome tent!