I have a hedge of pineapple guava that I planted 22 years ago. They are spaced 8 feet apart and most of them are at least 8 to 10 feet tall. I would not plant them any closer than that, as they are so thick now it is difficult to get in between them to pick up the fruit. They are Coolidge, Trask, and one other variety whose name I forgot.
We have a newer planting also that is entering year 4 that consists of Nazmetz, Mammoth, Apollo and Coolidge. We got the plants from Raintree, One Green World, and Menlo Growers. I would be interested in trialing other improved varieties but I don’t know how to propagate them.