All I did was make up a piece of of delrin to fit into the top of the spindle (actually its not the spindle but a shaft for supporting the pulleys I think) This piece had a hex milled in it to locate a nut then a slightly smaller hex below that, I then split it as you can see in the pic below. When the bolt is tightened it draws up into the Delrin and expands inside theĀ hollow shaft.
Hood