Creality CR-10 Dual Z axis belt tensioner

Belt tensioner for CR-10 with dual z-axis add-on. Using additional toothed pulley and belt as shown in the picture (ordered mine from Amazon, but any source should be fine) to synchronize the dual z-axis, i found the belt to be too loose, so I designed this simple adjustable tensioner that fits on the top rail of the CR-10, and adjusts using two M3 screws and 2020 T nuts. A 5/16 inch, 1 1/4 inch bolt fits the center of the pulley and provides room for a nylon or other locking nut underneath (o