The distinction between “supinus… pedibus pansis …et pedum digiti” for the circumference and “… a pedibus imis” standing into the square, means beyond doubt that the extended feet must naturally exceed the square perimeter, even more than with the toes.
About a century after Leonardo, two skilled portrayals of the Vitruvian arguments were conveniently separated by M. Perrault de l'Academie Royalle des Sciences - Paris 1684.
His figures seem decidedly derived from superimposition on that of Leonardo (please click over), with the little variant of closer legs, in order to touch with the toes the base of the square – although not drawn and visible together with the circle. But wasn't it rather a new compromise?: “hands and feet extended” in and out from those perimeters?
A non-functional measure, however – if not to introduce the implausibility of the hypothesis of Vitruvius – since even here the way in which the feet are extended, apparently consistent with the roman text, does not appear to be containable within the same circle theoretically valid for the arms, reaching it with the half of the feet which pass it abundantly with their phalanges.
It is time to make technical clarity.Let me resume the analysis from the basic plan, where the Leonardo's model looks restored into an exact square, defining the height and width of the standing body, with an implemental premise.
Trying to resize together the square and the circle does not succeed 100%; minimal adjustments trigger meaningful changes to the navel position, and a compromise is due. That's to say whatever change you do to the model could put off target your exact measurements.
I experienced this issue, but now, viewing the best resizing to the maximum extents of the circle and square and just to leave nothing to chance, it comes difficult to argue what might have happened to that paper!