Even the major fiberglass assemblies, like the decks and superstructure, are built to within half-inch tolerances over the length of the boat. The hull comes from Westport Shipyard, on Grays Harbor, which also produces complete yachts. That yard has enough capacity to make hulls for smaller yards like Eagle to finish. The key to this innovation is a hull design that works when lengthened at the rear. To make sure of that, the Sarin firm builds scale models of the hulls and has them extensively tank tested.
Further testing occurs when the boat is launched.
It must pass control and stability tests, perform emergency stops and starts, and perform as specified by the designers. Only then is it released to its new owner.