Yes interference and channel planning can be a big headache. I do have planned a section that will cover this but haven't finished it yet. I've typically gotten around interference problems by 1) using licensed (or at least not 5ghz, preferably full duplex) backhauls and 2) using AP antennas with narrow beamwidths (higher gain, less area covered.) I'm sure you're doing the same things if you've been doing it that long.