I had am of the opinion the stiffness of the single 8mm rod on the z-axis is not good enough, so I thought about using a single 10mm rod. However from converting the y-axis from 8mm to 10mm I had still two 8mm linear rods left over. The stiffness of those both combined is more or less the same as a single 10mm linear rod.. As weight on this specific modification does not matter I decided to go with these 8mm rods in a parallel arangement. In order to get the stiffness use greater 25% infill. I have discovered that the linear bearing bore may not be the right size, so check and potentially adapt. (SACD is appended) The bore holes for the linear rods have intentionally been made slightly smaller so that you Need to drill/ream them to the exact diametre.