So, rather than fight a losing battle, I just worked around him.
Here is what it took:
The tower sits on a 3450’ mountain that looks out over the San Joaquin Valley.
The majority of the affected 900MHz customers are east of the tower in about a 100* area that range from 2mi to 17mi. Threre are a series of ridges with no 900 users starting at about 3 miles from the tower extending to about 9 miles, then the valley opens up for 50 miles east to the Sierra Nevada.
Originally the integrated 900 AP’s were arced left and right covering around 150*. Users were connected to the AP based on angle.
I installed a 900 connectorized and a 12dB MTI 120* sector and used it as the “long throw” radio on 906 (the quietest channel), and aimed an integrated down into the valley as the “near” radio on 924 (noisy channel). After a few color code changes I migrated everyone to the appropriate radios.
Also had six 900 users on a third AP in an area covered by 5.7 so I migrated them over and turned off the 900AP.
No joke: I picked up 10dB or more on the far customers, and 6-12 dB on the near customers. It took a few service calls to upgrade and/or reloate antennas, however the phone has been much quieter and the graphs are much more stable.