If you have two horns: Reverse the baffles, so that on one cab the midrange is on the left and one it's on the right. Turn the top one upside down, and they line up (horns too).
If you have one horn: Consider the 15/6 + 12/6/1 cube model. The 12/6 cube set up such that if you tilt it one way, the horn and mids line up vertically.
Also, see Ukiah's pictures for how his 12/6 + 15/6 line up.
If you have one horn: Consider the 15/6 + 12/6/1 cube model. The 12/6 cube set up such that if you tilt it one way, the horn and mids line up vertically.
Also, see Ukiah's pictures for how his 12/6 + 15/6 line up.