3Drag Velleman K8200 new Z-axis rodends - Dual 8mm paralell rods

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.