Press Rail_Nut_assistant (see picture). And fasten the rail. The printed parts can then be removed from the beam. From the edges of the beam we insert M5_nut_holder (also printed from ABS), with M5 ...

You'll reuse the existing M5×30 BHCS and roll-in M5 nuts for mounting to the frame, as well as the 20T toothed idlers from the original stock Z idlers. 8× M3 hex nuts 8× M3×30 BHCS 4× M3×16 SHCS ...