Belt coming off tensioner

I finally got my car back together and running, but when I started it I noticed the belt was slghtly coming off the stock tensioner, coming close to teh vortech belt while running. When you turn the car off, the belt looks like it centers a little, but if you start it again, same thing. I was thinking either my tensioner might be going south, or possibly the belt might be a little long? The acessory belt that came with the s-trim was just to small, and had to get a 105 lenght belt, a little long, but it worked w/the car off. I'm pretty sure I've ligned everything up per vortech's instructions, so should I go down to the 104 size, you think that might help, or would the tensioner have anything to do with this if its going bad?

Thanks,

Just noticed something else, when the car is running the accessory belt seems to want to touch its other side that wraps around the water pump pulley. So I thought it was the belt, went down to the 104 1/4 size, but its really tight, I could barely get it on, would this be to much tension on bearings or anyhting? The tensioner looks like its almost maxed, might have moved a little.
here is the diagram for the belt:http://www.vortechsuperchargers.com/pdf/manuals/4FG218IM.PDF
its step 14, you can see the small gap in between the tensioner and water pump pulley, thats where they are wanting to touch with the 105.