It would be good to get some site testing and feedback on this actually.
Difficult to see the AMPDU aggregation, as I understand it is at the driver level. Even my dedicated wifi-sniffing-dongle did not show me the aggregation (as I don’t know where to look for the AMPDU size used.)
Need this type of counters, to make it easy: http://forum.mikrotik.com/t/help-mikrotik-capsman-wireless-download-speed-max-200mb-but-pcs-mobiles-link-speed-is-866mbps/142677/1