Richard,
If I had the space, I would go to 10' centers. But I don't, so I have done the following. Some are at 5' centers, in a row, with no bananas to either side, which still gives them some space to spread out. Some have been planted in triangular groups of three at 5-6 feet apart, again with no bananas near by. Some have been planted in groups of four in a sort of trapezoidal pattern. PLUS, They were all mostly interplanted amongst the pears, apples, cherimoyas, citrus, figs, etc, which were there before the bananas, and were on 15' centers originally, with more planted on the diagonals (which made for an effective 9' center arrangement). So the whole thing is a huge jungle. That's why I can have a picture of a banana flower hanging in a tangerine tree.
Lakatan, by the way. Fhia23 was in the fig tree and Thousand Fingers shares with the Apple tree. It is not a machete-optional zone.
Red Green with Grapefruit, Fig, Apple, etc in the back ground, and Fhia23 and Red Iho off to the side, and Misi Luki just out of th pix.