Please take a look on topics from Knowledge Base which can help you with final decision:
http://community.cambiumnetworks.com/t5/ePMP-Synchronization/Mitigating-self-interference-in-an-ePMP-ABAB-frequency-reuse/m-p/38203#U38203
http://community.cambiumnetworks.com/t5/ePMP-Synchronization/ePMP-GPS-Synchronization/m-p/37884#U37884
Thank you.