RE: Overproping a four stroke
This is true again.
But despite the shrouding provided by the duct, many modern turbofan engines have fewer, wide chord fan blades, replacing more numerous, narrow chord blades.
Examples are the Rolls Royce Trent and 535 series, GE 90, IAE V2500 and others.
They all achieve specific fuel consumption levels unsurpassed by any of the narrow blade engines.