Extended hybrid laminar flow control suction panels require significant internal airflow and pressure-drop control in their core structure. Triply periodic minimal surface sheet network core structures allow significant internal airflow, and functionally grading their surface-to-volume ratio enables passive pressure-drop control. This chapter conducts pressure-drop experiments on stereolithography printed panels to identify a pressure-drop prediction model that depends on the surface-to-volume ratio and the mean flow velocity. The measurement results show a significant correlation between the relative pressure drop and the surface-to-volume ratio of Gyroid sheet networks. Including a panel with a functionally graded surface-to-volume ratio also supports the possibility of passive pressure-drop control. A physics-based modified Ergun model is fitted to the experimentally obtained data, enabling the prediction of pressure drop in the fluid-mechanical design of extended hybrid laminar flow control suction panels.