I enjoyed reading your article and found it very informative.
My yard is all clay soil. You mention in your article "If you have the bucks, you can have a foot and a half of topsoil dropped on your existing lawn and then plant new grass seed and start over. Soil on top of dirt ain't bad."
I'm in the process of grading my land. My landscaper suggested adding only 4 inches of topsoil. Is that not enough?