Lew, I think that would be near impossible and might be better without the coupling. Isolating the motor unit from the arm would eliminate vibrations shared one to the other. On the other hand, outside energy hitting the platter or plinth would be different from that hitting the arm (board). There would be similarities, but I'm not sure if shared vibrations is a positive thing. Would micro detail increase or decrease?
In this case I see the value in the Halcro approach. I think it might be better, if executed well. Looking at the stock Victor plinth it seems like just a plywood laminate with a hole in the middle with 2 wood armboards. I think I can make a better plinth, but not sure I want to.
Regards,