Pruning a Hawaiian guava tree

In order to protect my guavas from fruit fly, I'm going to try putting insect mesh over the tree. Even if it isn't 100% effective, I'm hoping that it helps, because otherwise 100% of the fruit gets damaged by fruit fly and I can easily lose up to two thirds of the fruit to damage.

In order to put mesh over the tree, I need to give it a severe prune-back, so that it's smaller and I can train it to stay low by encouraging lower hanging branches.