I'd try fixing a control channel in UNII-1 non-DFS and 160MHz max bandwidth (post #21). All clients will connect at
their max bandwidth (mostly 80MHz or less) and those that support UNII-2a will connect at 160MHz bandwidth until RADAR/DFS forces them to drop back to 80MHz non-DFS. The fixed control channel will stay put and eventually force your neigbor to move away from it, avoiding Auto disruption of client connections. And the fixed 160MHz max bandwidth
will drop to 80MHz max bandwidth per DFS regulation, but it
will not drop further to avoid non-DFS radio interference... likely not a problem... and clients will still connect at
their max bandwidth.
Conventional wisdom is to set 80MHz max for better range/Tx power and no DFS disruption... although you may not need better range there.
That is how I see it and simplify it!
OE