the best location to place a tweeter is the point where the longest pathlengh from each speaker is available. This would be the kickpanels. This is due because frequency range from 200HZ and above are pathlenght dependent meaning that imaging would come out much better if the lenght of the right speaker from you is almost the same as that of the left. The smaller the difference, the better.

A negtive effect to this would be such that if the tweeter in the kicks arent properly angled, imaging would also suffer, also with staging and depth.