MeudtPG,
Not sure where you came up with 129.2 Lbs of force, the lowest spec I referenced is 140.5 Lbs of force, with the wheel elevated. That's factory specs. In my trial and error attempts to reduce vibration I noticed that the wheel in the air (with full suspension travel, not jacked on the rear shock mount) gains between 20-30 Lbs as the wheel hits the ground and the suspension squats.
If you read enough and talk to enough people, you'll come up with a lot of recommendations of between 140-160 lbs of belt tension on the ground. Many folks are going lower than the recommended 140.5 minimum in the air spec and having good results, some with and some without a vibration dampener. I had one point where I had absolutely no vibrations somewhere around 160 lbs, but I can't duplicate the setting at all. So I opted for the vibration dampener. Quick and easy fix, works very well (for me).