I noticed from the Martin Logan Owners forum that you have 13As. I've just ordered a pair but they won't arrive till January - I'm in UK.
Could you let me know of a dimension that's not on the ML site or User Guide? What's the distance between the front and rear spikes? I ask because my present speakers stand on 60 x 30 cm (23 1/2" x 11 3/4") slate slabs. I'm hoping these will be good for the MLs. My guess from photos of the side of the speakers is that the distance is about 49 cm (19 1/4") in which case I won't need to look for new supports. I have nice timber floors that won't appreciate spikes, so these slabs with a sound absorbent pad below seem to work well.