I don't really know the answer to your question because I am very new to this laser stuff but I have the smaller 12 x 16 laser and it is very well built. The bed of the machine is lightweight honeycomb aluminum that is supported on a metal tray. I would think that if the weight is distributed evenly on a larger machine it should work, but perhaps some of the owners of the bigger machines will have a better answer for you.
You might address your question directly to one of the companies selling Chinese lasers. Rabbit, Red Sail, etc. There are guys on this forum who sell these machines and are very helpful with information.
Jacqui, Goddess of Chaos, GSOLFOT