Rich, I did not mean to lead you down the garden path. For what it's worth, I did find the MKII stock mat to sound just fine, even though I did like the SAEC a bit better. The 2A mat and the Denon DP80 mat are both thicker and more rigid than the MkII mat, and the Denon mat does color the sound compared to the SAEC. (I have more experience with the Denon.) Please don't feel you have to go out and buy a different mat from stock. As to the question about mats and servo mechanisms, there was a thread on DIYAudio where this was discussed in connection with building a new power supply and electronic control for a MkII. The servo is "tuned" to see a certain platter mass. If you increase the platter mass too much, there is a danger that the servo action will be overdamped. If you decrease the platter mass by too much, the servo will go a little nuts because it is getting inadequate feedback. The unknown for any particular system is how much mass is too much or too little. The Technics tables have powerful motors, so it is possible that they will be quite tolerant of heavier mats, esp the Mk3, but motor torque is not the only parameter that would govern the outcome. As far as I can tell, the SAEC mat (wt given above by T-bone) does no harm to the operation of the servo on my Mk2A. It sounds good on my Denon, too, but looking at the strobe on the Denon with the SAEC mat in place, I think I may be able to see a very slight wavering of the speed, back and forth. Can't hear a problem, however, and it may be just my imagination, it is that subtle. But some of the very heavy mats, such as many of those sold by TT Weights, would be a no-no for a direct-drive turntable, IMO. TT Weights would probably custom build you a mat for a dd, however, if you specified the mass in advance.
Interestingly, the Kenwood L07D has an optional platter ring, which increases the effective mass of the total platter assembly by quite a bit, and all the added mass is at the periphery where it has the greatest possible effect. To compensate for that, the L07D Power Supply has a switch which changes operation of its servo when the platter ring is being used. This kind of proves to me that the phenomenon is real, not just theoretical.
