I have a hard time believing that a 2 1/4" spinner is too small to cut for a 14x6 prop - although truthfully, a 2 1/4" spinner seems small for a 60-size plane.

Are you sure you're measuring it at the back of the backplate?

In any case, don't forget that you can (and should) enlarge both sides of the existing slot.

You want to remove the blue area in the picture below.