I think its more in the base size... 7.75 square... + center of gravity. No way these should be on a stage with PA gear... which I think is how they are advertised! I was expecting them to collapse, but they are holding the speakers just fine. Caught one of my cats eyeing it for a jump one day.
Thankfully that hasn't happened yet to my knowledge. Truthfully, I would expect the thing to topple if Iggy jumped there from the drafting table he likes to hang out on.
Larger base, and heavier, if I did it again. Totally... say 15"x15"x3/4" MDF (for the weight, hell, maybe even laminate two pieces together!) Countering whatever weight you put on top is best. Clearly, though, I still didn't trust the top either.