The ornamental design for a double plinthfurniturelegdesign, as shown and described.
FIG. 1 is a perspective view. FIG. 2 is a top plan view. FIG. 3 is a bottom
view. FIG. 4 is a front elevational view with the rear elevational view
being a mirror image thereof; and, FIG. 5 is a left side elevational view
with the right side elevational view being a mirror image thereof. The
broken lines which define the bounds of the claimed design form no part
thereof.