Sota owners -- help needed re: reflex clamp

Are you able to use the rubber washer if your Sota turntable has vacuum hold-down?

I recently purchased a Sota reflex clamp for my Star turntable (with vacuum). I cannot achieve a vacuum hold if I use the rubber washer that the instructions say to put under the LP. So I use the clamp without the rubber washer and have no problem achieving a strong vaccum hold.

Am I getting the benefit of using the clamp? Without the rubber washer there appears to be nothing for the clamp to "reflex" against. I intend to do some detailed A-B testing after I become more familiar with the new tonearm added at the same time I got the clamp.

Thanks!
Terry