Unfortunately GK put the feet on the wrong side. They should be on the short side to give a tall cab and better dispersion. You can rectify with a cheap set of feet or shift the stock ones.
True. I have stacked my CX210 the "tall way" without feet. I gained a little height but not much, since the speakers are arranged diagonally. I didn't notice a difference in sound either, but will probably experiment a bit more.