The AMSDU trick doesn't work for me. I still notice some sort of WiFi instability (need to switch my device's WiFi connection Off then On again to restore the connectivity), plus my Braava robot still can't connect to my AP.
Very nice to read that!
But the WRT1200AC is equipped with a 88W8864 chip, which makes this router different to the WRT3200ACM on a hardware point of view. Your custom builds won't work for me, as far as I understand.