The Badass XC belt everyone is selling is a KRX length belt, it's about an inch longer which will give you around 5% reduction but the problem is the stock secondary will not close far enough to keep constant tension on the belt, on most machines the secondary is fully closed with the KRX length belt, this can cause shutter on some machines especially with a heavier load.
We modify the secondary to close further and keep constant tension on the longer belts, we can even run the much longer ProR belt for 15% reduction however because of the diameter of the secondary it runs really high but thus far has not been a problem on the machines we have been testing it on.