Studiosoundman:
A lot of what you say makes sense, and I found that the simple steel spikes that come stock on the B&W 803d to be essentialy useless. But I might not have discovered this had I not had the problem of the stock spikes penetrating my rather thick, dense plush carpet. With that carpet, I need penetration well beyond 1 1/4" to 1 1/2", due not only to the carpet but the thick underlayment pad beneath. To be effective, the spikes must penetrate to the wood flooring surface. Add to this the stability problem. We have earthquakes here in CA, and a little shaking can send these topheavy B&Ws crashing to the floor. Even bumping them during vacuuming can produce unintended consequences. Ever wonder how may G's that $1000+ diamond tweeter will take before its damaged?
So I was looking for a stability solution as well as a sonic one, and extensive conversations with folks at Maple shade and EdenSound convinced me of a number of things.
(1) Its not just the shape of the spikes or the material they are made of, but the MASS as well. Brass spikes intrinsicly coupled to huge masses of brass are best. If I could afford 2" thick brass plates under the speakers I would use them, but at the current cost of brass (and cosmetics), that solution is out of the question.
(2) Spikes have a sonic "diode" effect, transfering unwanted cabinet vibrations to the surface they are imbedded in. This can be a bad thing if they are in concrete, as unwanted reflections back up in to the cabinet are possible.
(3) The use of thick, natural wood platforms of maple have a damping effect, and give you added sonic "sinking" if sandwiched between groups of massive brass footers.
So in my final implementation I got the stability I needed with a sonic improvement I was not particularly seeking, but am happy with nonetheless.