Does it matter which way you twist the belts? There are two ways of doing it - clockwise and anti-clockwise. A better way of understanding this is at the middle of the belt between the motors and the front idlers, are the teeth facing upwards or downwards. And if it matters, does it have to be the same on both sides?
I can't see why it would matter, and I'm just curious.
Also, in this thread (http://eclips3d.proboards.com/thread/51/share-eclips3d) I see a couple of cases where there appears to be a twist along the front span - look at the second picture by jhopiv and the first by macgyver03.