@Wisefam22 a 5 inch is plenty, I do not see the harm on having a bit bigger than what you need. Besides spending more money and using up a bit more energy from the batteries, I personally do not see the harm on having a bigger screen.
During the 2017 crossing my 3 backups "failed". The ipad will not turn on, the inreach explorer was to small and so have the VHF screen. During the storm ( and even during the entire trip) my 7inch Garmin was the only navigation tool that I was comfortable looking at. It is amazing how something that looks more than enough on land, becomes useless when you are being tossed around. It is highly unlikely that we will bring our boat on the 2019 crossing, but the next time HMS Artemis 553 makes a crossing we will most likely have another chart-plotter for the copilot. Unless I get something that I can use up my jetski, I will most likely get 7 or 9 inch.
Most people will say that having 2 plotter is an overkill let alone 2 seven inch ones. But I believe that our boats have no business crossing the stream and defiantly not with me at the helm. So anything that I can do to increase the chance of making it 57 miles east, I am going to do it.