Milos,
The advantage of taping across the belt is the same as cutting on an angle. It lets you avoid vertical joins or material boundaries. Those can cause a thump, or at least some microscopic slippage, when they encounter tight bends like the motor capstan. Making the cut and taping on an angle greatly reduces that problem.
Good advice about just making a few belts. Getting a feel for it is really all it takes!
The advantage of taping across the belt is the same as cutting on an angle. It lets you avoid vertical joins or material boundaries. Those can cause a thump, or at least some microscopic slippage, when they encounter tight bends like the motor capstan. Making the cut and taping on an angle greatly reduces that problem.
Good advice about just making a few belts. Getting a feel for it is really all it takes!