Darn. I guess we're just not having fun and spontaneity. And I was just beginning to believe we did! Learn somethin' every day! ;-)
In theory I agree with Lloyd. OTOH, adjusting height on a rig like an MMF (or even a Walker) wouldn't work for us. That's why we went for a rig with SPONTANEOUS, FUN, VTA-on-the-fly. We're eatin' our cake and havin' it too.
Unfortunately that's not doable on an MMF budget. :-(
Billbo, your notion of a quick mat change rather than dragging out the hex keys makes some sense, but IME (and we do adjust for every LP) the benefits of VTA optimization require a finer adjustment than any mat change could accomplish. Large VTA adjustments often have little or no sonic effect. Tiny adjustments within the very small sweet zone for any particular record have a large effect.
Mat-swapping just isn't subtle enough, and therefore I tend to agree with the others on this thread. Choose a mat you like the sound of and set/forget VTA for now. When/if you can spring for a rig that makes it easier to do, I'll take sides in favor of doing so.
In the words of my amp designer, "Enjoy music, tolerate equipment."