Thoughts on improving the rigidity of cheap Chinese 3020 engraving machine?

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What do you think about this design? flaws or possible improvement points? I have CNCEST 3020t but want to make it a little bit more rigid, to avoid long machining time of aluminium;

I think about using PA6 or PA13 L beams 100x100x10mm of 600mm length each to mount y axis to them;

base I think I would pour with about 50kg of Epoxy-granite which is composed as follows: (8-16mm granite stones 23%, 2-8mm granite stones 30%, play sand 35%, epoxy EPODEX 12% all percentages by weight) and vibrated for several hours.

double ballscrews SFU 2005, with nema23 steppers mounted using HM15-57 brackets with FK15 and BF15 on y axis and linear rails - HGR25 with 2xhgw25 carriages on each side

hgr15 and sfu1204 on both x and z axis (MBA10 with FK10 to mount screws to Nema23 steppers, BF10)

800w 24000 65mm spindle with ER11 collet.

gantry is composed of 30mm thick PA6/PA13 plates bolted together.

T-slot table (which I already have) of size 240x430mm, 30mm thick