Of course there will be an "improvement" when you go to the bigger feet. This stuff has become so subjective and so uncontrolled (in the scientific sense) that there is a huge placebo effect. If you are prepared to like it, and if your turntable does not actually fall to the ground, then you will like it. This is in no way meant as an insult to you personally. It's just a part of this crazy hobby.
I see your larger point, Lewm, but really I'm not prepared or fixin' to like any particular kind of configuration. True, I expect the larger feet to make some difference--why shouldn't I since I'll probably end up paying a chunk of change for them?--but whether I prefer that change or not is up for grabs. After all, they'll be easy to sell. Placebo probably would play a larger role if one couldn't sell after trying.
I take a very practical approach to this plinth(less) issue. My table didn't come with an attached plinth, and since I found it to sound pretty darn good without it, I'm sticking with it for the time being and trying out closely related configurations. I can honestly say that if I had some plinth ready to hand, I would immediately try it out to see what difference it makes. I take it that Chris's and Raul's point is to suggest the converse: if you have a plinth, take it off and see what happens--you may be surprised.
In my opinion, that minimal kind of experimentation won't settle the larger debate, but it might transform one's picture of the debate. However, I agree with Dertonarm that even if we had many hands going up saying that their experiment led them to believe plinthless is better, it would still leave a rather large hole in our understanding of why that is (if it is at all). There should be some 'reflective equilibrium', as the philosophers say, between observed findings and theoretical explanation. Pure theory and a rhetorical reference to 'physics' and what it allegedly tells us is pointless when it flies in the face of repeated observation; conversely, 'mere' observation is empty because it just gives us data points without a theory to tie them together.
At any rate, Yahoo Japan is not easy to navigate. Are there any other options to find these feet? I've been perusing Hi-Fi Do Japan. Very cool site--but alas no feet as of yesterday.