I have a 4 foot wide by 2 foot deep by three-quarter inch piece of wood on top of mine. Sitting on top of that is probably about 30 to 40 pounds of equipment. The legs support it just fine but it is a little wobbly. I have it pushed up against the wall and that solves the problem. If it were standing in the middle of a room it would be too wobbly. You’re looking at a much thicker top so perhaps that would provide stability? But your top is much larger than what I am working with as well. I think you are wise to be cautious.
By bugslug321