Hi,
actually i didn’t really understand about the problem. When reading the linked threat, there’s explained not to use single band router to connect to main router via wifi AND use wifi for clients, because it’ll reduce the possible wifi-speed.

So i thougt you want to use one AR300M for connect WAN via wifi to main-router and 2nd AR300M to connect the client('s) via wifi. Seperate the two wifi ways to arrive best performance, rite?

If so, you should disable the SSID in AR-300M#1 and connect the clients only to AR-300M#2’s wifi.

Actually i thought the AR300M and also MT300N (which i own) are made for mobile usage to get possibilities not speed. I’ve bought it for hotel-usage with captive portal + WG-VPN to home.