I think I'd mount the two Alpha 10's one on top of the other, physically close together. I'd put a crossover on each Alpha 10 driver, but I might consider staggering their values. If they are allowed to both reach 1.6kHz, then you'll have three sound sources in the octave around 1.6kHz or so. So I think I'd proably crossover the bottom woofer at 200Hz or so, and then let the upper one reach all the way up to 1.6kHz. That will prevent them from cancelling harmonics above 200Hz, but I'm not sure the push-pull arrangement remains effective as frequencies go up anyway. I'd expect shorting rings to work better through the midrange, and push-pull arrangements to work better in the bass.