I have my M3 Turbo S’s on their spikes on a thick rug over a wooden floor on a concrete basement foundation. The important thing is that the compression tweeter is at level for me. I was thinking of resting each speaker on a stone/marble or a hardwood slab, but that would elevate the tweeters.
is there a reason the speaker can’t be tilted up ? Shimmed with plank of wood at 90 degree to the legs to start. Once the right angle is found, go source longer spikes from Bolts Plus that will give you the height you need at the front.