The ornamental design for a multipurposeflatchassisvehicleplatform, as shown and described.
1. Multipurpose flat chassis vehicle platform
1.1 : Perspective
1.2 : Front
1.3 : Back
1.4 : Right
1.5 : Left
1.6 : Top
1.7 : Bottom
The parts shown by means of broken lines in the reproductions are not part of the claimed design; the shadings in the reproductions represent contours only and do not illustrate an ornamentation or decoration on the surface of the product.