It may be a bit counter to oft-used mantra,but its a lesson we learnt long ago transitioning from unifi's seamless-handover to non years ago:
Use the exact same channel,but drop the strength of each AP till they are almost imperceptible to one-another,and set the min-rssi accordingly
The same frequency reduces dead-drops in the connection switching frequencies when changing AP (remember the battery drain cell c 4g used to cause? Sameish premise)
the unifi articles state to have the aps on different channels and to drop the power.Tested and works well.Obviously alot of it depends on the clients but as mentioned wifi is a dark art at the best of times.
