The on axis vertical response of line array will always show a peak but go off axis and you see problems. This is true regardless of c-t-c spacing. Perhaps you are ignoring the off axis performance.
Furthermore, you don't say what you do to accommodate the loss in sensitivity (less array gain) that occurs when you space greater than a wavelength apart. If you take frequency response measurements, you'll see both the impact of combing and the loss in array gain.

Jim