An external occulter is a spacecraft own along the line-of-sight of a space telescope to suppress starlight and enable high-contrast direct imaging of exoplanets. The shape of an external occulter must be specially designed to optimally suppress starlight; however, deviations from the ideal shape such as manufacturing errors can result in loss of suppression in the shadow. Due to the long separation distances and large dimensions involved for a space occulter, laboratory testing is conducted with scaled versions of occulters etched on silicon wafers. Using numerical simulations for a ight Fresnel occulter design, we show how the suppression performance of an occulter mask scales with the available propagation distance for expected random manufacturing defects along the edge of the occulter petal. We derive an analytical model for predicting performance due to such manufacturing defects across the petal edges of an occulter mask and compare this with the numerical simulations. We discuss the scaling of an extended occulter testbed.