I think I have reached the end of this project minus the cover which will have to have some modifications to it.
I got one of the 3D adapters for Magura RT8 on the P4 , fit good but for me lacked stability because of the material and I wanted 3 point connection not 2.
I got one made out of 1/2” aluminum then fit it on my bike and drilled out the 3 hole.
It fit great and super solid.
Next step was reduce it to 3/8” thickness and reduce some material.