I endorse this thread, however I also want to know exactly what Banana Porridge is.
As for bananas in general, I really hate them to be too green, I like them with a bit of brown on the skin, but not so much that when you open them up the actual banana is covered in random brown squidgy bits. I would probably favour a 6 on your banana chart.
However, Bananas contain a lot of potassium and taking too much of this is as bad as eating too much salt so you shouldn't have more than 5 bananas a week. Also the more brown a banana is, the more potassium it has. Apparently.