Once the cradle is in place, then all other parts of the binder will be aligned to it referenced to the trough bottom of the forward side of the cradle. This is where the drive belt comes out. The centers of the bottom of the support troughs need to be the same distance from the binder as the cradle trough is. On the parallel plane to the binder face centered on our reference point all guide wheels and the drive wheel . Word about drive wheels.
Most wheels are too shallow and the drive belt easily jumps out of it.
This is also true concerning the pulley that holds the weight. I have switched from a small one to a larger one that has a good deep wheel. I found a ready source for these at my local hardware store. I disassemble two wheeled pulleys for my guide wheels. Now for the placement of the first guide whose position is very important and its misplacement will cause problems.