I haven't read all the posts, but if dimpling propellers and leading edges actually improved efficiency, wouldn't manufacturers already be doing it??

Surely Boeing and Airbus would be dimpling leading edges if they thought it would improve aerodynamic efficiency by even a fraction of a percent; that's all winglets improve by, but when you're talking 10,000 kgs of fuel burnt in an hour (B747), then a fraction of a percent makes a huge difference over the life of the aircraft.