DIY turntable plinth material

IMO, the better VPI platters seem to work very well with MDF. In particular, the Aries and Classics are great performers. That might be an easy and inexpensive place to start. It might also be a good idea to figure out a good set of feet or suspension. That will make a huge difference in performance.

Have you considered the armboard material and how to mount the armboard to the plinth (if that's your plan)?

From personal experience using a TNT1 platter / spindle / bearing and motor, a 1" acrylic plinth and 1/2" armboard bolted to the back right corner made for a good performer, but did leave room for improvement.

One issue that I ran into was that the original TNT bearing extended well-below the plinth top surface. Took a re-think of the feet.

Planning to use my Finite Elemente Compact for feet, they offer tremendous performance. I also have some BDR jumbo puck and cones I can use as well.

I'm not familiar with the bearing and spindle assy for the platter you're using. Make sure that there is adequate clearance between the top of the plinth and the bottom of the installed bearing to clear the shelf surface. Also suggest that the plinth should be at least 2 inches think. Laminating 3/4" MDF is rumored to work OK.

I made a slate plinth , used a Lenco motor and idler system, stacked the VPI Superplatter over the Lenco platter and the result is one of the most slamming turntables I heard, very close to my EMT 927 in terms of dynamics .
http://www.lencoheaven.net/forum/index.php?topic=803.0
The VPI TNT is far behind !
Good luck with your project !