I have made an interesting discovery in my specific situation that is worth passing along.
Layout:
Wifi link from a remote DSL link that connects to the WAN interface on a gargoyle router. Using ubiquiti wifi radios
In the past, I have struggled to use QOS with ACC in this setup. The unreliability of WiFi links would throw off the ACC logic. The fair limit would not track load at all, but rather random connection issues.
Recently I discovered a way to overcome that! There is a setting in ubiquiti AirOS under "advanced" tab for "aggregation". It is the setting for how many ethernet frames are combined into a single transmission. The default is 32 frames or 50,000 bytes.
By lowering that setting to only 10,000 bytes instead of 50,000 I was able to get ACC to work as expected across the Wifi link!
My theory is that the extent of buffering was throwing off ACC. When noise would occur, the link would fail and slowdown, causing ACC to decrease dramatically. This is normal for Wifi of course. BUT, when there is a 50,000 byte packet, noise has a much greater effect than when there is only 10,000 bytes. At the lower setting, noise does not impact the transmission nearly as much and thereby ACC works.
Lowering it more than about 10K causes loss of throughput at the bandwidth I am using. Too much overhead when streaming small packets!
Nevertheless, lowering buffering made a profound difference in the operation of ACC, so that now it is useable!