Hi, Charles,
I practice the pedal harp in bedroom shoes, bare feet, or “whatever,” but then perform with regular leather organmaster shoes. Â (Just before a performance, I DO practice a lot in the organ shoes, since they do feel a bit different, particularly the higher heels!) I have never experienced the squeaking you mention. Â Have you tried the silicone spray yet? Â I have used it to stop every other kind of squeaking, so it should work.
Best wishes on solving this problem,
Balfour