when looking into harmonics, generaly you want the second and third harmonic the most. they tend to be the smoothest and most beneficial of course it all depends on the motor. i have tested my first design and found the the harmonics all wrong but the but even worse was the return harmonic canceling some resonance. i am looking (and working with our audio engineer) to try to find the correct balance for this engine. even the suzuki stacks had some cancelation but it was limited because of small size. i will try to update more often on how this is going.