That's an experience of "how may sound some Widor on the Walcker ?". IMHO, it works fine.
The III geigenprincipal was used as the gambe asked by the score, and the I doppelflote as the flûte harmonique.
Widor is mainly praised for his brilliant pieces with many notes and strong rythms, but he also knew how to write fine music with few notes and few stops.