Continuing the discussion from How does loading and running programs work:
whatever you use to raise the machine’s feet, it has to withstand strong bending forces in horizontal directions. A piece of wasteboard, mostly made of MDF, that has only the size of the machine’s foot, is not really suited for that since the work forces may compress the material. MDF is too soft for that, at least such a little piece that can not transfer the forces into the surface.
Possibly you could make a wasteboard as one bigger piece that is able to take the entire machine including the feet, in this case I would use the minimum recommended thickness as explained in the manual (2½" – 3"), nothing less. But then replacing the wasteboard would require removing the entire machine.
You are not alone in wanting to use more space than the distance from Z to machine feet’s base. Usually you would have to build a strong frame, which should have steel or strong aluminium profiles that go through from front to rear, at least under the two Y axes, and screw or weld these to some construction of steel or aluminium profiles underneath. Here is a machine with an aluminium extrusion profile frame with removable aluminium wasteboard:
You see, making an open frame allows you to work on higher workpieces.
Such solutions are mostly wanted if you want to place a bigger workpiece, possiby on a rotational axis, under the machine. What I plan, is to weld a U-shaped machine base from steel profiles, with a floating wasteboard that can be removed if necessary, but which (in contrast to the two images above) is also open at the front and the rear, in order to work on pieces that are longer than Y dimension of workarea.
If the workpieces you want to use are smaller than the workarea, you could also buy the QCW Frame and remove some of its beams in the middle.