The 24" c-t-c distance I was talking about was vertical spacing of the mid/woofers, which is less than 1 wavelength at any crossover frequency between 300 and 400 Hz. This is why I thought I could get away with only 4 6.5" woofers per side evenly spaced in a 6' line. Am I misunderstanding the driver spacing guidelines in your white paper, or do these guidelines not apply at lower frequencies?

Thanks very much for your input,
David