most single stage out there now look pretty good without clear, It's works and gives a little better DOI,but if all he's going to do is a little clear in the last coat i wouldn't do it, if it needs buffed there's a good chance breaking through the half coat of clear, Single stage is usually pretty high solids and putting a couple coats of clear on top of that gives more than ideal film build. If you want the clear i'd switch to base