I try never to talk buyers into a bike. I present the bike, let them take a ride, and make their own decision. Sure, I talk up the condition and components of a bike, but the ultimate decision is the buyer's. For some reason, he is considering/looking at a carbon bike.

If you have a steel bike, you might show him that and talk up the benefits of steel. Its always helpful to have multiple sizes available.

To me, he does sound too heavy for a glued carbon frame. You might want to try the Clydesdale list.