Passing by here, I came across this post. This was the organ that I found completed in the workshop when I first encountered the builder and the workshop in September,1990. The first time that Bernard used a full length 16ft Principal is in the case of St Louis-en-l'Isle, Paris. It is to do with the proportions of the Golden Section and thus - as rightly pointed out - the five bottoms notes play a Stopped and a Quint. One is not at all conscious of this when playing as the voicing is impeccable. The Quint & Tierce provide a sound simiar to the Berlin Philharmonic double basses. The 32' Napoléon was added a few years after the opening and is so called after the founder of the modern-day Vichy, Emperor Napoléan III who, along with his son and wife are buried in the Crypt of Farnborough Abbey in Hampshire. I trust that this answers a few of the querries.
Nigel