Too bad there remains so many questions about plinths for Technics and other quality DD tables.
On one hand we have Albert Porter who found sonic delight with ever more massive plinths for his series of SP-10 tables. And the fellow who restored and built new plinths for mikel favors high mass designs. Jweiss has experimented with SP-10 plinths for a few years and his current preference (in slate) weighs about 200 pounds I believe. And if you look at the plinths designed by Technics engineers for their own tables, they increased the mass of each succeeding model for the first three, with the fourth only slightly less than the third.
On the other hand we have Raul, the leader of the pack for plinth less set ups. Apparently Raul began with a massive stone (marble? If so, I agree with Lew that was a poor choice because of the higher resonant frequency -- it rings folks!) plinth, then changed to a single sheet of wood just large enough to support his tone arm, while the motor unit was supported by AT feet. Most recently he eliminated the wood mount and now has his arm freestanding of the SP-10 motor unit. A few others also report pleasing results with plinth less set ups.
Now among those who favor massive plinths, there seems to be one point of agreement. Using only MDF gives poor results. That material may work for idler designs but not for DD, at least the SP-10 series. And I think that points up the importance of the resonance characteristics of the material(s) chosen. Some have tried Corian plinths and I've read criticisms of that material as well. The MDF is slightly dull sounding and damps dynamics while Corian is usually bright with an upper frequency emphasis.
My own experience is very limited. When I got an SP-10 I mounted it on a single sheet of particle board (no one recommends that), simply to provide a platform to mount a tone arm. I will say it sounds very good. But building a better plinth has been long delayed due to finding someone with the tools to help in construction and multiple design changes for what I want.
At this point I find myself in full agreement with Lew. First, I wish someone could report on a comparison of an appropriate massive plinth directly against a plinth less set up. And second, given the critical importance of proper alignment of the stylus tip relative to the record groove, I cannot understand why someone would mount their arm independently from their table, thus giving up the mechanical integrity that a coupled mounting provides.