Good info, thanks.

Even just looking at what you called losenging, the full diagonal brace is much more effective than multiple cross corner ones (which are similarly effective as webbing).

Regarding damping, I think it is critical. You can make something stiffer but without a means to dissipate energy it will only ring at a higher frequency. I've used two methods for low frequency damping.

The top beams (two long ones have the Y rails on them) are made of two steel box sections bolted together with a 3mm layer of butyl tape between them. This is what I meant by layer damping. It converts the beam flex in to sheer strain against the damping material, so is far more effective at low frequencies than just a surface treatment of 3mm butyl tape. My Z axis plate is also dual layer with damping between.

The second method I have used for low frequency damping is to pour the 4 main upright box sections with concrete that was mixed with something called 'SBR'. SBR comes as a liquid that gets used in place of water in the concrete mix and cures as latex rubber. This is used commonly to provide damping in concrete structures for reduced foot-fall noise and such like.

https://www.researchgate.net/publica...city_of_cement