Take this for what it's worth, I have an engineer friend that works for Gates. He told me that as a result of modern manufacturing techniques and process controls virtually all belts of the same part number are "matched". With the exception of an alternator locking up I've never actually had a belt fail.
Get together with your buddy and smack him upside the head for buying into engineered arrogance.
I threw a pair of Gates belts on the Power Tour.
I threw a SECOND pair of Gates belts on the Power Tour.
My pulleys are in alignment. Tension is set properly. Engine accessories are not angled.
I put the belts on and you can watch one flop more than the other.
Both times I threw the belts it came after releasing the throttle at high rpm.
The belts are not a perfect equal length. Either the width or the length is varying by just enough to prevent equal loading.
