My stands came with a handful of small (maybe a cm square) rubber bumpers that adhere to the top plate and keep the speakers from scratching against the metal of the plate. I thought I'd have to use some sort of adhesive, but what I've found is that over time the weight of the speakers kind of squishes into and bonds with the rubber all by itself. They're certainly not impossible to tip over, but harder than you'd think.

M22ti mains, EP175 sub, VP150 center, QS4 surrounds