Cutting the hole in the bottom of the fuselage for the sump tank vent tube. This is one step in a long day of visualizing, forming and fitting vent lines. Needless to say, not all were perfect; and one tricky section had to be scrapped and reconstructed.
While he was working on this, he noticed that we hadn't installed the fuel drain valve. Brett reminded us that drain valves sometimes leak and need replacement; and he once witnessed Rene Dugas performing a drain valve change at Rough River.   Good catch, Brett!   We decided to enlarged the drain valve hole so that the socket will fit; and this simple change means we won't need to remove the sump tank to change out that valve.