I recommend the Technics 1200/1210 extra thick mat sold by KAB USA. It sounds the best on the previous generation Techie 1200 /1210 up to the Mk7 model. I personally own a M5G and use the extra thick OEM mat and a 3/4 pound (approx 360 gram) pound spindle weight. My spindle has the upgraded KAB wax material under the spindle bearing housing, coupling it to the base plate. This directs platter and other acoustic noise down the spingle to the base not so much up the cart and tonearm.
With the wax "spacer" mod, additional weight of the spindle bearing and housing is better supported when coupled to the baseplate. I oil my spindle bearing using KAB's recommended oil approx every 100 hours of play time. In the decade plus of ownership, I've had no issues with my spindle bearing getting noisy or wearing out.
Using a clamp would worry me as noted above it pulls the spindle upward where there is minimal support, logically chance of damage exists if excessive force is used. Platter mat and spindle weight use is system and listener and system subjective, perceived audio benefits change with different LP's being played. Obviously, anything that flattens excess warpage, better coupling a warped LP to the platter is preferrable.
Keeping the tonearm playing with minimal horizontal and vertical runout allows the cartridge and styli to better trace the grooves, resulting in a more positive listening experience no matter what combination of turntable or upgrades being used. This minimises cartridge/cantilever suspension wear and/or suspension damage, resulting in decreased cartridge wear and higher play hours on the cart itself.
Periphery rings are also subjective, having their time and place for use. I've yet to see a ring being sold which correctly the Technics 1200/1210 due to their design and layout. An LP with excessive vertical runout will benefit from ring and weight use when it comes to playback quality. A flat record may or may not benefit from added spindle weight or periphery ring, the same as it may or may not benefit from thicker or different platter mat composition.
A thicker mat decreases VTA and changes VTF slightly as the arm is raised. This is often perceived as a sonic improvement, and may be not from the mat construction itself but a change of VTA VTF or SRA by raising or lowering arm height. A minimal change in SRA/VTF/VTA can often place the stylus in that optimal operating corridor and stylus angle, resulting in superior sonics overall.
Ideally adjustable VTA 'on the fly' allows the listener to make incremental adjustments to SRA when using thicker/thinner LP's and platter mat changes in height. The perceived positive change is not so much from the mat material/ weight or album thickness itself. Obviously, those changes are a more complicated subject for a different thread. Remember, the sum total of the turntable components and its adjustments within the system itself are typically more important than just any one component or change.
This can be complicated subject, frustrating many because they don't understand the supposed dark arts of turntable setup No matter what the overall component combination is made of everyone makes mistakes along the way. Keep learning from them and your experiences until you get it right. Once you do, you will have repeatable success that no matter what cart, arm, mat, table combination you choose, the audible results will be overwhelmingly positive.
