I recommend a heavy flat stone ore a fitting flat piece of marble with thereunder lead bitumen. Lead bitumen makes the contact better with the speaker and normally doesn’t destroy your speaker on the upper side (at own risk).
But ehhhhh, I have some cd’s on them most times ()
she insisted on putting stuff on top of my energy veritas towers
they have rubber top caps that are slightly rounded.. she scratched em and i wasnt happy
so i put them away .. and in their place is kef 105/2 no grills
so that leaves the mid/treble enclosure exposed they mount at an angle not level
heres what we have now
but no longer on my speakers