I'm liking these ideas.
You could combine the two ideas.
Drill the small 3W/DA hole pattern, two of the holes are for the anti-rotation pins on the BME hub, then just use 4 pins in the other 4 holes between the prop and spinner backplate.
You don't even need to drill the holes all the way through the prop. Just drill from the back of the prop deep enough to leave enough of the pin protruding into the spinner backplate.

Thanks for the tips guys.

Jim