So good news! The stand takes the weight I filled it to about 95% but turns out I didn't level the base well enough so got a bit nervous and emptied it out super fast by hooking it up to the swimming pool pump (had a 2mm height change from front to back and 5mm from end to end) so I'll get some shims under the legs and get more water into it when I get home from work in 11 days but at least it's a bit less stressful now!