Aluminum is obviously weaker than Ductile cast iron but as far as I can tell the Aluminum is the way to go and these are my reasons. Ductile cast iron will heat up alot faster and as soon as these housings are sussepted to wet grass with the kind of heat they hold this will start surface rust that will work into the bearings over time. Aluminum stays cool and dosn't rust. I know aluminum is weaker but a new housing thats aluminum is around $70-$80 a new cast iron housing for the equivalency size mower is around $300-$400 Are these thoughts correct ? Do you agree?