I recently added the zero-pound springs to my rears. Over time, the spring started rubbing through the shock body on my Ridetech shock bodies when they unloaded, to the point that I sent them back to RT and had them rebodied. These are simple to install, although not exactly a cheap solution, and they allow full droop on my setup without unloading the spring.
You also need these:
It ends up being about $160 for a set for the 2 rears...
Here they are installed and assembled:
