Record clamp/weight and turntable speed

Don't know where you've been for the past 400 years, dover, but "proper" never has meant "reflex" not in any dictionary I have ever seen. But I tell you what, since you want to argue so much, find me the clamp you think is "proper" as described above. One that clamps the record down so flat and secure it has to be lifted by the edges after playing. You find that one for me, post a link like I did for mine. That way I can explain in detail what you missed and why it is, compared to mine, not a proper record clamp.

VPI.  Screw down with threaded spindle.  Washer between the platter and the record.  Mine was a TNT 3, (25+ YO design). I had to lift the edges to release the record.

I still miss that table, sorry I sold it.

It depends. I’m not familiar with the Herbie’s Mat. How thick is the washer? Does it rise above the level of the mat?

By far the most effective way to clamp with a washer is with a threaded spindle and a tapped concave bottom clamp. This allows sufficient force to flatten a record against the platter and effectively create a vacuum between the platter and record. However, if you don’t have a threaded spindle, you can try something like the Record Doctor clamp and see if that works It has the right kind of bottom, but has a tightening mechanism that uses friction in order to hold the spindle. You would have to exert some degree of downward force while tightening it to get the same effect, if you can even do that.

VPI clamp: https://cdn.shopify.com/s/files/1/0105/4542/products/vpi-deluxeclamp-3_1800x.jpg?v=1571265214

Record Doctor Clamp: https://www.audioadvisor.com/images/RDRC_BLK_BTTM.jpg

Edit:  I believe also the Sota Reflex clamp does something similar with friction, but as you snap the lever down, it grabs the spindle and moves the weight downward to clamp the record tight.  I can't find a picture of the bottom, but you can add a rubber ring around the periphery if it doesn't have a concave base.

If you still have it, I'd use the original washer that came with the VPI.  It was designed to work with the clamp, both thickness and stiffness.