Recently, I attended a seminar but I can't for the life of me remember which sensei taught. But anyway, he did mention seeing Osensei's feet. Osensei used to wear tabi/white socks... and the dojo tatami although clean did leave the tabi dirty somewhat. But what was surprising was that the only part that was dirty on Osensei's feet was his ball of foot at the point closest to his big toe.
This doesn't exactly answer your aikikai/yoshinkan stance... but I've used both, and to get the weight on that particular point, I was more comfortable using the yoshinkan stance. With the Aikikai stance, I felt that more weight was distributed on the blade of the rear feet.