I added the two holes closest to the motor.  They along with the original pulley holes (closest to the tonearm)  are used to through bolt the plate to the plinth with 5/16-18 bolts (the hex heads have decorative caps) torqued to about 10 ft-lbs. There are opposed 5/16-18 stainless button head bolts underneath with stainless couplers in the center of plinth. There is old data that suggests that cast aluminum unlike extruded (such as 6061) when under compression the dampening factor can double or triple, and at 10 ft-lbs each bolting (total of four) applies almost 2000 lbs clamping force each. Also, the plate is in no load bearing path, providing the maximum benefit.  

I did the plinth modification with a little change as possible and to allow bolting just in-case I did not like the sound.  But the improvement in sound was good - The TNT was known for throwing a large soundstage, with the plate, it just got larger in all dimensions.   After the installation, tapping on the plinth in-play eliminated any response through the speakers, and I liked the aesthetics, the black-silver motif is now carried throughout the table. 

I will post some construction pictures tomorrow so you can better see the AL-plate.