You can reduce jitter on your link by dropping maximum mcs on the offending radio. Look at the performance stats, find where the mcs is jumping around and set it at the lower value. You will see latency flatten off.
I run dual 80's then drop mcs individually on each of the 4 radios until pings are stable. Aim for 99% of traffic to pass at a single mcs value. The ping spikes you're seeing are the radio trying higher mcs value, failing, then retransmitting on a lower mcs - by dropping the max mcs you stop radio from trying the higher mcs ...
By doing this I've ended up with a solid 800/130, and current load on my nw peaks at 500/60, so customers always get the full speed of their plan when they speed test, and latency is almost acceptable - empm3000 latency still high but it's improving with updates and better config by me.
good luck
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