Thanks for the replies guys.
I've tried to hunt down thinner hub props, but they are much of a muchness really.
Fizzwater is right about te measurements, it's a M5 size prop shaft, that makes things a touch more difficult as I have tried to find prop nuts etc in that size and there is no luck over here, seems Australia doesn't deal much with 1/2A stuff.

Anyone know who sells the cone shaped nuts that will sit inside the prop washer that Fizzwater spoke of??

Seems odd that there is so little prop shaft.