in my opinion it woulod be a neat thing to do but would be a waste of money, unless of course you are talking about mounting a turbine engine, then we're talking. Ducted fans are just a ****load of low pitch blades on a hub that gets spun really really fast. You have to think about some things here, why invest money in a ducted fan when it is going to be more maintainence, weigh more(engine, fan housing, all the gear) when you can have a simple prop creat the same amount of thrust??