I have basically the same setup, but I was not able to get AT&T to add the Netgear LB1121to my family plan. The only thing they could set me up with was an additional stand alone 10GB plan which isn't much.
The 7" will fit the flat area but just barely. I wanted to add one there, but it only gives you about 1/8" up and down to play with so I decided not to try it.
I went with a Garmin GPSmap 9" with new Fusion stereo and remote and 210ais VHF. All works great together via NMEA2000. It was the biggest I could fit without doing some serious fab work. I really like it. Before and after pics:
Did this last weekend. I made the hole 1/4" larger and dropped in a stainless cupholder. turned out nice. kinda harder to see as I was doing a lot of other work, but its just to the right of the controls where the old Clarion remote came out.
Same switches on mine are used as an on/off switch for the remote amplifiers turn on leads (usually single blue wire). One amp powers cockpit, the other the cabin.