Hey Mikes,
adding a second layer of wasteboard is what Onefinity will tell you, they tell this in the setup manual. But it is a design problem, this is what I tried to express with my post with the comparison to other Z assemblies on other CNC machines. My solution will be to replace the Z assembly with a more standard one as shown in the upper video. See also “Universal Z axis” and “Z axis assembly” in this forum.
By the way Tom @TMToronto, with who I discussed this topic from beginning on, succeeded in making a completely new Z assembly with his Onefinity CNC.