Overview, what we will do is to first gather the data from your existing Range Extender/Camera network. It will be needed to fill in the boxes in the Router config screens. Armed with that knowledge, we configure the router to mimic your stock extender.
1 - Normally you start with a working Vision WiFi Range Extender setup, power up the extender, the Vision, then your Phone/Pad and go to Settings>WiFi, and connect to the Extender Network.
2 - While still in the phone/pad WiFi settings, touch the (i) info icon to the right of the currently connected Range Extender network. In this information page, jot down the "IP Address", "Router", and the "Search Domains" information.
3 - Now Open the DJI Phone App and go to Settings>General>Binding. In here you will see the "Current Binding" data. Copy down the SSID number, this is the hidden ID of the Vision Camera, note that it's "FC200_the last 6 digits of its MAC address", just good to know. Note - The other instructions I saw had you reset the Extender and then Re-Bind the Camera using the QR Code from the shipping box and the manual (pg16), this should not be necessary if you have a normally working system already as you should be able to just read the current data. I have tried it both ways and it does work to get the Camera's hidden SSID number to show up if that information is blank in this screen for some reason.
Now we will configure the router. But first, I thought I'd mention something about using a second, spare, Range Extender. I was going to get a 2nd extender to modify it with big antennas etc. as others have done. I took the 2nd extender and found that I could bind it to the same Vision using the QR code from the Vision Shipping box (I keep a copy of this QR code in my carry case). The 2nd Extender shows up as a 2nd network on the iPad. So you can carry a spare extender and use one OR the other with no changes needed on the Vision, just connect to the which ever extender you need, each has a unique network name, easy!