Hypereutectic ductile iron is a potential candidate for lightweighting of commercial castings; however, it has been found that the high cooling rates in thin (less than 5mm) sections promote the formation of carbides and pearlite, impairing ductility and the casting integrity. In the present study, ductile iron plates ranging from 1-5 mm in section size have been cast and characterized to determine the minimum section size that will retain suitable properties. Structural characterization is undertaken by optical microscopy, quantitative metallography and ultrasonic testing to determine ferrite/pearlite ratio, carbide content, nodule count and nodularity. Mechanical properties are determined via tensile testing of specimens machined from the cast plates, and additional elastic characterization via ultrasonic analysis. Cooling rate as a function of section thickness is modeled using MAGMA software. Finally, microstructural and mechanical properties relative to section size are used to model local mechanical properties and eliminate unnecessary material.