Supply Chain
Cones stand upright to protect the package, and that forces a square grid — two thirds of the footprint, at best.
— no.
Limited by whichever of height or weight binds
Cone base diameter is used for both the grid and the footprint, which is right for spacing and slightly pessimistic for utilisation since a cone tapers — the space above the base is partly recoverable by nesting the next layer down over the cone tips, a pattern some mills use and which this does not model. Stack height should be checked against the crush resistance of the bottom layer rather than a nominal limit, particularly for soft packages. Stability in transit depends on wrapping and on the pallet overhang, and neither appears here.
Yarn Cone Palletizing Geometry & Load Optimizer — free, with the formula and a worked example, at Textile School.