AiMesh config question with AC86U and AC68U

I'm currently using an AC68U as my primary router with several media bridges (AC66U, AC56R, Buffalo H1300) around the house connecting via AC wireless. Unfortunately due to the internet entry point, the AC68U is on one end of my long rectangular house. The farthest media bridge (AC66U) is on the far end of the house from the router and up one level. A typical connection Tx/Rx rate is reported as 234-351 Mbps.

I'm planning to add an AC86U to my home network. I originally intended to replace...

AiMesh config question with AC86U and AC68U