Looking good, classic design. Ballnut brackets off gantry plates may need a bit of support?

I’ve always ordered from aluminium warehouse as you can select the exact size you need. Other members have mentioned cheaper sources elsewhere (Smiths?).

I tried to keep 21deg C for the epoxy pour but from my brief experience with it I wouldn’t be concerned going down to say 18. I guess the heat might be required more at the beginning to keep the viscosity lower for the self levelling as it should generate its own heat as it cures. Others may have more to add on that.