Syncro Unit for Ender 5 Plus

One obvious weak part of the ender 5 plus is the lack of 100% synchronicity of the two Z-steppers. Over time the orientation of the build plate got skew.

Solution was to couple both motors, since this I haven't to care about this issue.
Positive side effect is, that I can move the plate evenly (when motors switched off) just by pulling the timing belt to left and right.

Pictures show left and right side, on the right I lasered a scale (4mm = one turn, paper print also can) and printed an arrow, so I can see the uniformity of the bed (ABL) while printing.

Parts:

A) 2 x Pulley 60 Teeth GT2 - 6mm (ali)
B) 1 x Closed Timing Belt GT2 - 6mm / 950mm (ali)
C) 2 x Coupler as shown in FreeCAD-Drawing (3d-printed or lathe (POM, Alu))
D) Headless screws 4pcs M4x5 + 4pcs. M5x5

Preparation:

A) Open the inner holes to 14mm dia (lathe), this should fit together with the outer diameter of part C)
B) Can be used as bought, 950mm is the correct length, when the distance f