It would take engines in the .90 to 1.20 size to run those props.

I don't know why OS recommends these ridiculous props sizes for engines. Either it is a way to make low noise requirements or a very silly marketing strategy. With people checking specs on engines, they may think that saying they operate on the big props must mean they are stronger engines. Pure bunk. If they were torque monsters then they would have very long strokes and small bores, known as a "under square" design.