I have a RatRig v-core 3 400 and I had trouble / did not like the original with the printed 90 y_max_endstop_block thingy and the y_max_endstop_angled_endstop.
For some reason it did not work for me and never was solid.
With this y homes nicely and I safe 1 screw and t-nut too ;)
The author hasn't provided the model origin yet.