A couple of questions I have, then, if you don't mind:

+ Playing with the machine as it stands, there's a lot of resonance from the hollow sections of the profile, for the Y profiles I intend to either fill with sand or maybe epoxy/granite. With one end almost closed at the front and the significant vibrations from the less than stellar 1605 ball screws these are resonating like an instrument at the moment. I'm sure this will hurt surface finish as I can clearly feel the transmission through to the spindle by hand, but I expect a sand fill will help since these parts won't need to move.

+ With regards the Gantry, I'd imagine filling that with epoxy/granite will be much too heavy for my motor/screw combo (480oz/in plus double nut 2005 ground ball-screws). Has anyone any experience with filling the voids of profile with expanding foam to dampen vibrations/resonances? I suppose I could test a piece but I don't have any spare material to hand. I wonder if something like silicone fill could work if it could be done cheaply enough.

+ Also would be keen to hear any input from the idea of bolting this entire CNC to a concrete wall, specifically how I might line everything up in practice. I like the idea of gravity pulling away chips and using less floor space but could just go for the traditional setup.