This is a mount for large NEMA17 motors. Tested it on 48mm. No additional idler pulley needed. This mount is also suitable for wide 9 mm belts and 10 mm pulleys.
No supports needed. Please, use the PrusaSlicer screenshot as a reference.
I also added the version with pins for better stability. It should be printed from the opposite side. Cut out the holes for screws and belt after print.
See also
This work contains two parts: this Y-mount and Y Axis Tensioner for 9 mm belt.