“Topping” a tree is not a professionally accepted practice for reducing a tree’s height or volume. It can damage or even kill a tree. Cutting major leads or limbs off at a set height results in a proliferation of “suckers” at the cut. These suckers are much weaker than natural growth and can result in problems as they grow.
In proper tree reduction, cuts are made leaving a “leader” so suckers do not take over at the cut. Often expressed as a percentage of the tree, reductions of over 30% are not recommended. If the owner wants more than that, a tree removal may be the best solution.
This results in a tree that is made more resistant to storm damage and will continue to grow strong and healthy, with a balanced pleasant shape. If you want a tree “topped” call the power company, not an Arborist.