USRSA: At any given reference tension, the stringbed stiffness will be lower on a lockout stringing machine (those using a spring-tension system) than on a constant-pull stringing machine (those using an electronic or drop-weight tensioning system). Different string materials and constructions, and different racquet head sizes, will require different amounts of compensation to match the stringbed stiffness produced by a constant-pull machine to that produced by a lockout machine. For racquets wi