Hi Vily - thicker steel is better than adding concrete. Keep making things as big and thick as possible. The z axis is what will let you down so make it very stiff. So on that point here's my thoughts. 1) you have the conventional z arrangement on the front of the gantry 2) I have done this twice and have concluded that the saddle is a constraint (and a pian to design) in this config. The 8 bearings and plates make for a cramped design. Plus you want to be able to get to the bolts to check them or retorque them without having to pull the front off to get at the heads 3) this also means the spindle is mounted way out in front of the gantry so it has a big overhang So 1) I mount the gantry rails on top of the gantry 2) this allows the Z axis to be mounted closer to the gantry reducing the cantilever 3) this also means the Z and X bearings are separated and can be accessed easily and the saddle can be designed so the bearings are supported directly on webs which make it very stiff. 4) that's why I like a flatter gantry vs a tall gantry as then the Z does not have to reach down as far with the "bracket" saddle. cheers Peter