I know rigidity in the Z-axis is a big issue with the MPCNC resulting in recommendations of it being no bigger than 81mm.
I had an idea but I do not have the knowledge to know if this would improve, not help, or make worse Z-Axis rigidity.
What if the four legs were stepper motors with thick lead screws attached and the whole machine was raised and lowered rather than using the existing Z-axis machinery in the MPCNC?
Just a thought, curious what the answer is from people more knowledgeable about this than me.