[GeeTwo]

Originally Posted by jkelleyrtp

What does your belt path look like inside the tube? I get that chains have the dual sprocket but I don't know how to do it with belts without doing something really strange.

You could use two 9mm belts within the tube. If you routed belts like you have pictured, you'd want to be careful to make the sides mirror images, as the system you show would be more efficient at accelerating to the right than the left, as the tensioners would take up relatively slack segments to the right, but tight segments when accelerating to the left.