New Serpentine Belt and Tensioner - Yet a Loose Belt?

[TonyI]

Installed a new tensioner and serpentine belt and the belt is loose, not tight across all pulleys. I checked if I missed a accessory pulley or deflection pulley and all is right. I l Looked up both the belt and tensioner part numbers against my car model (2008 535i N54) and they both check out fine (at the manufacturer). It's like I need to:

(1) Go to a smaller belt? (can this be an option?)
(2) Unload the tensioner? (doesn't make any sense)

Any insight from the veterans out there?

Thanks,