The Allures 44 is considered by many to be a "blue water" monohull. Certainly, the French take them everywhere on the planet. Jimmy Cornell swears by them also. One is pulled out at the yard here.
They have two small rudders, separated off centerline and canted to accommodate heeling. The rudder size is within close approximation to our catamaran rudder size (and the Alpha 42's) - around 24-30" deep and with similar chord length. They are built on a 2" shaft. I do not know if it is solid or of what material (it is not carbon).
Mark