An RF signal processing system including multiple drop-in modular circuit blocks is disclosed. The drop-in modular circuit blocks include input and output launches exhibiting the same launch geometry. The RF system may include a conductive plate with a grid of holes disposed on the conductive plate. Multiple modular blocks may be installed on the conductive plate to form a cascade of modular blocks that exhibit common launch geometries. The cascade may include an RF probe with a projection and conductive pin that overhang a portion of a launch of a modular block at an end of the cascade. Flex connects may be disposed on, and held in position by, anchors to connect adjacent modular blocks together in a prototype system. A production RF system may exhibit the same overall geometry as a prototype RF system to speed up the transition from prototype design to production design.