I'm going to disagree big time here. In the various forms of shizentai (natural stance) your weight is between the feet and the paper thin wedge under the heel sounds about right. From this stance you have an incredible amount of mobility. Of course during the thrust in any of eight directions (basic Shodokan unsoku practice) requires weight to be shifted to one foot or the other but the whole foot does not have to be firmly placed on the ground. Moreover, that shift is only transitory during the moment of the thrust. Shizentai is maintained immediately after the thrust and of course after the movement is completed.
Tsukuri one of the most effective means of rapidly closing distance is in effect a planned, off-balanced, lurch. You just finish in ----- you guessed it shizentai.
I doubt very much anyone can move nearly as effectively with one of both heels firmly placed.
Kevin Wilbanks wrote:
Sorry Brett, but that sounds a little crazy to me. Since there is no way to put most or all of your weight into one foot with the heel slightly off the floor for more than an off-balanced moment, that pretty much limits you to stances where your weight is somewhere between both feet. While this may be a good position for cranking and twisting, it's a position of virtual immobility. In order to step or slide, you need to be able to let your weight sink completely into one foot, probably mostly in the heel or in the mid-foot. If you don't plant your whole foot, or at least mostly solidly through the heel, you simply can't move, except to lurch or stagger. The only other way to attain some balance on the ball of one foot is to raise up into a ballet postion. This is just basic physics.
In general, I would say since mobility is what makes Aikido work, nitpicky details about how one stands two-footed are more important for quasi-static and slo-mo drills than for actually doing business in a dynamic scenario/event. In a fluid situation, one's weight will almost always be on one foot or transitioning from one to the other.