I am looking at improving the prop hub assembly on my Hummelbird. There are so many spacers all of which can create vibration and other problems on their own. The bolts involved tightening down the prop are 4 1/2 inches long. Starting at the prop flange extension of the crankshaft there is a wooden disk 3/4 inch thick which clears the big hub bolt. Then against that is the prop. On top of the prop is the spinner mounting disk and on top of that is another wooden disk 3/8" thick. Finally an aluminum disk 1/4" thick sits on that which is all bolted together with the six 4 1/2" by 5/16" bolts. All these disks are joined with drivers [aluminium tubing about 1/2 inch dia.and about 1 inch long- 12 of them] Would it be better to remove the two wooden spacers and mount the prop against the metal flange and the aluminum disk on that. Do you need drivers? Friction and the bolts on their own should keep the prop in place. How are other Hummelbirds set up?