The Bibliothèque nationale de France is where the Paris Manuscripts, the manuscripts in which the double hull design appears, currently reside. During the Italian capaign, Napoleon took many of Leonardo's works from Italy and sent them back to France. Although some of Leonardo's works were sent back to Italy after the end of the Napoleonic Wars, for example The Codex Atlanticus, most remained in France.
Source:
“The Strange Vicissitudes of Leonardo's Manuscripts.” UNESCO, 3 July 2018, en.unesco.org/courier/octobre-1974/strange-vicissitudes-leonardo-s-manuscripts.