RT-AC68U / RT-AC68P / RT-AC1900 / RT-AC1900P continued

I'm linking to this thread over on SNB but was told I should ask here instead since that's mainly ASUS / Merlin and not Tomato.

http://www.snbforums.com/threads/rt-ac68u-rt-ac68p-rt-ac1900-rt-ac1900p.35759/page-4#post-299410

My initial questions summed around...

RMerlin said: ↑
BCM4709A0 is fine, it's the C0 revision that requires a newer SDK.
OK. THANK so much for the replies!

Now here's the rub in the...

RT-AC68U / RT-AC68P / RT-AC1900 / RT-AC1900P continued