The link you shared seems to be for rear Timbrens and this thread is about steering? Did you have Sumo's in the front, as well?
If you are talking about rear Sumo's, they are actually 3000# per spring. What is more important than that is what they are made out of.
Sumo's are made of very dense progressive closed cell foam as opposed to rubber in the Timbrens. I've used the Timbrens in the past on company fleet sprinters and they were too harsh.
I have several Winnie View MBS owner friends jealous of my ride with Sumo's all around. Very smooth and stable. Other MBS owners with Sumo's on this forum will agree as well as on the Sprinter forums.