Too much belt tension will create a lot of drag in the tail drive system. Too little tension will create belt slapping on the boom. The N5 does not need an ultra tight belt, try to achieve a medium belt tension that does not cause boom slapping or create excessive drag. The N5 belt has an XL tooth profile so skipping teeth and slipping should not happen. If the belt is setup correctly you will not even know you are flying a belt driven tail. After flying a belt driven tail on my N5, I never want to go back to a torque tube. The simplicity and durability are unbeatable.