I'd like to know what the difference is between slo fly and e props. Other than the obvious, looks. My son in law has a NES Mamba and the prop shaft is barely long enough to get the nut on with a E prop. I compared the 9X4.5E to the sol fly 9X4.7 and the slo fly seemed too flimsy for the Mamba. Whatcha think??

perhaps you could get a prop adaptor to go on the shaft? is it a direct drive motor or a geared one?

You've already observed the difference: Looks, and weight. The Slo-Fly prop is meant for slow-flyers, anything that would use a GWS prop. Thin Electric props are meant for higher power applications.

As BadSplice alludes, you can get a longer prop adapter.

What Matt said along with this:

If you didn't figure it out, slo-fly props are designed to be spun at low rpms. They push a large volume of air at a slow velocity. This, in turn, makes the plane fly slower. They are more efficient at creating thrust, which is why they are used.

E props, on the other hand, spin fast pushing a low volume of air. The plane will fly faster because of this. They are used a lot with direct drive configurations.

I forgot to mention that the choice of a prop depends on your motor and whether or not it is geared. It is best to do what the manufacturer of your powerplant recommends.