I'm surprised PBCF isn't more common. It essentially reduces swirl and cavitation in the central vortex, converting it into additional thrust while also reducing shaft torque. It's an inexpensive retrofit (payoff time <6 mo) with broad compatibility, and the swap can be done while unloading with no downtime. And yes, it reduces rudder surface erosion which is caused by cavitation.

Seems like a no-brainer. Maybe folks just aren't aware of the technology?

https://www.youtube.com/watch?v=a8PjWSeLUzY