Yes the efficiency will suffer. A great deal of the design of excellent props goes into reducing the tip losses. Also, the hub to blade transition will occupy a greater percentage of the usable propeller shape - useful prop thrust area - just wasted.
And yes the prop will run at a higher RPM, so it is important that the motor has a KV rating that supports that function. And if you take care of that; since the motor will be operating at a higher RPM, you will probably want to use a lower pitch prop.
All of this is nicely taken care of using bench thrust testing stand - one of the finest tools I have constructed in my electric flying career. So many fuzzy problems seem have clear solutions with thrust, rpm, current and wattage information. ... I copied mine device from the one advertised by BP Hobbies.
And you don't even have to have the perfect prop for the testing process... getting data from similar, as well as larger and smaller props will allow you to make a very close approximation of the near-ideal setup. It is also entertaining fun
I have found that I shouldn't mess with the shape of high priced, high quality props. They are so good that any change is very likely to reduce the efficiency.
Richard, Good luck!