The original plates work fine, but I managed to loosen one of the wheel bolt holes by using too much force while installing them,and now it doesn't have very good tension. So had the idea of using M4 bolts as tensioners for the bolts/wheels.
Needs 4 M4 bolts and nuts.
Note: haven't tested this yet. Probably won't be printing these because I'll just try drilling holes for the M4 bolts on my existing plates.
OpenSCAD source: https://github.com/spegelius/3DModels/blob/master/PrinterParts/Tronxy/Mega_gantry_remix.scad
I used 3 perimeters and ~20% infill. PLA