You will need a Gates 508C Sonic Tension Meter on setting number 7
Tighten the X-Belt Tensioner fasteners in even increments until the target tension is reached.
Always ensure measurements are taken at the middle with the X Carriage in the middle; measure the long portion of the belt (closest the lower smooth rod). The portion of belt being measured should not contact anything while being measured; this will cause inaccurate measurements.
Once tension on the belt is properly set, cut off the excess belt from both sides of the part but leave approximately 10mm protruding from the motor side. This allows for grip should the belt tension need adjusted post-assembly.