I'm using them without supertweeter. They sound (to my ears) better than 902s on 511 or even tractrix. BTW those were GPA dias in the 288k's that were measured.
I suggest you to measure 902 on 511 with the crossover than the 288, keeping the exactly same measuring conditions (distance, mic placement, amp gain etc). Using ARTA's overlay function you'll probably find out more about sound difference between those drivers.