How good is the Obsidian plinth of Technics SP10 ?

I've got an SP-10 MK II with the original obsidian plinth, dust cover, and EPA-100 tonearm. It is not yet set up. I'm toying with several options for an alternative plinth, but the answer may be as simple as keeping it stock except for filling the inside of the cast aluminum TT housing with epoxy mixed with brass powder. Some have stated that the obsidian base subtracts LF.

I'm a believer in Stillpoints in some applications, but in the case of an SP-10 Mk IIa in the obsidian plinth, three pairs of good ears had difficulty detecting any meaningful difference between stock footers and Ultra SS.  This may have been because the plinth was sited on a substantial 4" maple base. Much more improvement was heard with a 4mm copper mat on top of the stock alum platter.