Record clamp/weight and turntable speed

Try no weight/clamp.

You'll need MyMat for the above

I have the Herbie's mat now. Without a clamp, the warped records (those I have) tend to skew the sound. 

Study carefully the pictures on my system page. Especially the platter and record clamp. https://systems.audiogon.com/systems/8367 Nobody makes a proper clamp so I had to build one myself. It has been improved since these pictures were taken but the key features are the same.  

Two main features: the thick washer that fits over the spindle, and the under side of the clamp is dished out. Really need to take more and better pictures because this subject keeps coming up.

Look at the thick black washer placed around the spindle. This holds the record up about 1mm above the platter surface. The clamp is dished on the under side. Clamping the record down causes it to bend very slightly, forcing the outer edge of the record down onto the platter. Because of this virtually all records, unless they are pretty obviously warped, they lay perfectly flat. In fact they are so flat and flush with the platter that when the clamp is removed after playing they continue to be held down by atmospheric pressure until gently raised at the edges. So freaking cool you have to see it to believe it!

To the best of my knowledge the only other one to figure this out is Paul Beckett. He designed a variation of this into his Onkk Cue platter. The Cue platter is very slightly dished so that as the record is clamped down it contacts the outer edge first. A better engineered approach, I must say. If I had a machine shop with a lathe it is what I would do. But I don't, so we make do with what we have.

So that's what you do. Take my washer/clamp idea and figure out how to make it work for you. 

You provide no actual information.  How heavy is your record weight? What type of turntable do you use, belt-, idler- or direct-drive? Does the motor incorporate a speed control? What type? Have you actually measured speed with vs without the weight?  If not, how do you know that the speed is not affected at a level you cannot detect simply by listening for pitch, which is what I presume you do?  If you are concerned about your own record weight, you might consider switching to a record clamp, like the SOTA.  A clamp applies pressure to the LP against the platter mat surface but adds very minimally to the weight supported by the bearing.  Some don't like clamps because there is the potential to transmit noise from the bearing into the LP surface.