Start with dimensional inspection of aperture position, face flatness, perpendicularity, locating features and damage against the controlled drawing. Check burrs, raised plating, particles, dents and corrosion around the aperture and locating surfaces. Cleaning cannot repair displaced metal or an out-of-tolerance face; define reject and approved repair limits before assembly.
Support converters, cables and long sections so their weight does not distort the joint. Use a documented seating, fastener sequence and torque method, and protect the aperture while hardware is open. Control gasket or seal compression and flange clocking. Record any condition that changes the reference plane, including shims, adapters or an alignment fixture.
Quantify repeatability by measuring a stable verification device or through path across deliberate disconnect/reconnect cycles, preserving complex S-parameters and environmental conditions. Compare reflection, transmission and phase rather than one scalar reading. If connection spread consumes the measurement or product margin, improve the locating, support and assembly method before accepting the component.