Thanks for posting that up. I went there and registered just to see. Found the short vid on adjusting the belt, IMO the man is way off. First, he measured the belt at the top, that is not accurate. Second, if he can "feel" 10 lbs of force with his finger the man is better than me. That's like being able to feel 10 lbs or 120 inch pounds of torque with a regular wrench instead of a torque wrench.
For what you have to pay for the belt tension gauge, even if you only use it once or twice a year, I'd rather ensure the proper tension then be wrong with my finger and end up having to buy either a new pulley or belt or both. I haven't looked at the rest of the site yet, but I'd take what this site says with a grain of salt.
I could be wrong but all my training and experiece tells me that to accurately measure the "slack" in a belt or chain for that matter, you never take the reading from the top, you aways take the reading from the bottom. You will always have a lil more slack on the top strand then you will the bottom so by his method, the belt will be even more tight. Like I said, I could be wrong but that's how I was taught to adjust both belts and chain. Take care. T