These 4 hours happened over two days, and started with the riveting of my brake pedals. These are specified as A5S (stainless steel) rivets and they are heavy duty. I used a $5 rivet puller from Aircraft Spruce, and when the mandrel finally releases from these rivets, they really shoot out the back. Warning to other builders: Wear eye protection and always point the back end of your riveter away from people or things that you care about. Beyond that, most of the time was spent cleaning and painting the center spar and a bunch of other cockpit parts.