I'm having the same problem with my 2007 OR X.
I know I'm putting some extra weight in the back, about 400lbs, but I do have to transport this and can't afford to have another vehicle.
So, I ended up calling the RAS people and I have a set on the way. According to them, it should increase the payload by 50-70%. He said it shouldn't sag with up to 50% more weight, and shouldn't bottom out with up to 70% more weight.
Plus all the other benefits they claim.
So we'll see. I'll let you know how it goes.
aa