In Florida, nobody here keeps any grove trees over 3 - 4 M any more. The big citrus and avocado growers have them mechanically sheared and topped. The sides are angled at 15 degrees. More trees per acre and higher production. They are also less likely to go over in a hurricane. The smaller growers are following Richard Campbell's lead and keeping their trees below 3 M. They are so much easier to maintain like that. It takes a little getting-used-to because you have to keep the trees a little "hungry". Nitrogen is the enemy with this kind of culture.