Good bit of kit. We're just putting one on a large rib. We have a cox & a navigator station at the console so it's a bit crowded. It's huge though and very deep. From memory I think you need around 6" behind the panel if it's panel mounted. Otherwise you need lots of room above a console if your mounting on the tilt mount.
I too have an E120 and have linked the simple NASA AIS engine to it. Although I have only used it to "play" so far, I can see it being extremely helpful in poor visibility. Splitting the screen in two and having chart on side (maybe with radar overlay), radar the other and having AIS targets shown on both with MARPA to track "interesting" targets, I have a very good chance of not being hit or not hitting something!!
One case where AIS proved useful last year was navigating up the Tamar river - I was able to "see" round the bend that two of the big harbour tugs were heading my way. I moved to a suitable position to one side as I rounded the corner to see these two with a very big navy ship between them! It wouldn't have been a problem, but it was just nice to know and have some extra advanvced warning.