Markd51 pretty well nailed it above. The VPI washer/clamp system sounds very similar to the one on my Gyrodec and the key is to get an even distribution around the perimeter of the clamp as you install it and NOT to over clamp! You actually require very little rotation of the clamp to eliminate most warps and effectively couple the record to the platter.
With 180 and 200 gram records, take the washer off and don't use it but still use the clamp and do NOT overtighten.
I know the Michell clamp comes with no instructions (as a result many people upgrade-unnecessarily IMO-to the much more expensive Orbe clamp and threaded spindle) and it sounds like the VPI one doesn't either. Would be good if both Michell and VPI would include some written instruction on this as it's important.