And a similar result would see them move nine points clear of Grenoble, who play at London Welsh 24 hours later.
Left wing Fainifo was in scintillating form and ensured Stade maintained their undefeated record against Italian opposition in the Amlin Challenge Cup.
Prato have made a fight of their home games so far and were unfortunate not to secure a bonus point last week after scoring three tries against Stade.
However the odds are against them pulling off a major shock in Paris.
Prato have only once managed to concede less than 50 points in their previous seven games on the road while Stade Francais are unbeaten this season at Stade Charlety.