Yes, you have 2x2 = 4 elements but since they are arranged on square lettice (am I right ?) on both principal plane they act as a 2x1 linear array, so my previous commnet is still valid !
you can hope only on the element beam taper (have you the elelement pattern ?) but chebyschev is not applicable in your case because, as I have already explained, you don't have real side lobes...
In summary, how can you control side lobe level if you don't have side liobes ? that is the problem.