The ornamental design for a stabilityplatformboard, as shown or described.
FIG. 1 is a perspective view of a stability platform board, showing our new design;
FIG. 2 is a side elevation view thereof;
FIG. 3 is a front side elevation view thereof;
FIG. 4 is a top plan view thereof, the bottom plan view being identical thereto; and,
FIG. 5 is a perspective view of the stability platform board depicted in FIGS. 1-4, illustrating the attachment of the stability platform board to four stability platform ball elements.
Although only the top plan view is shown, it will be appreciated that a bottom plan view of the stability platform board is substantially identical to that which is illustrated. Furthermore, the broken lines depict environmental structure and form no part of the claimed design.