Pryso, I can't tell you constrained layer or multi ply birch are superior with the SP10 MK2, I've not even completed mine yet.
Audiogon member Vetterone has done a LOT of experiments with plints. You can contact him via the Audiogon server by looking up his name.
My experiments with my Lenco proved to me that heavier plinths were superior to the lightweight original. I wish I had gone even heavier with the Lenco construction, so I intend on going over the top with the Technics.
I think the Technics with plinth and arm will be close to 100 pounds, we're even adding brass plates to attach the arm board and a brass plate in the bottom to draw energy from the direct drive bearing in addition to the other materials in the plinth.
From what I've read on the internet by tweakers, the MDF is a blessing and a curse. Some like it and some don't. To read about some of these projects, go to Google and type in Garrard 301 plinth, Technics SP 10 and Thorens Plinth. After clicking links and multiple pages of each search, you will likely find more material than you want to read.
When my arm arrives I'll do nice photo's so you and everyone else can see how my project is progressing. I've studied several dozen photo's and I suspect my project will look somewhat like what others have come up with. You can't deviate too far and fit the table :^).
Here's a very popular page on Technics, you may have already been there.
http://www.soundfountain.com/amb/amb.html