Albert, are you using the Stillpoint Ultra's direct to the carpet? I was considering a set of 4 of the Alum. model for my Parsifals but wonder if that would work direct on the carpet as opposed to carpet piercing spikes.
I'm not qualified to answer, I've always had my isolation products (Grand Prix, Stillpoints, etc) on a hard floor.
I suggest calling Paul at Stillpoints and ask his advice, no doubt this comes up every day for him. If you get an answer please post here so I and everyone else can read.