Convergent or baffle cone is a lot more involved with many factors 2 b considered, but there's heaps of literature out there on this subject. Usually "about" 2x diffuser angle is used.. Center section's (length) function is simply 2 provide correctly timed wave seperation. Stinger ID (Bell) is 58% header (beginning) for Hi RPM, 62% for Mid Range Torque, with 60% best all round. Stinger length is 12x Header (beginning) ID. Cheers