My suggestion would be to borrow some props and try them. It's all a bit of a dark art in selecting the right one. On paper a given prop might well be ideal, but in practise it rarely is. Don't ask me why! I guess that there are many factors involved.
When I selected my prop/props for different boats I've have I gauged prop performance on my cruising speed at a given RPM and chose the prop based on the fastest speed it could push me along at say 3000/3500 rpm. Obviously you need to check that the prop runs in the recommended WOT range too.
Have a look at the prop thread Here
and see if there is anyone with a prop that suits you and would be willing to lend you. You might have to pay some P&P but might help you sending hundreds of pounds in the search of the holy grail.