Well, since we have used the same mold (Steel) for decades... hard to see where it would be of a different size, but maybe a slight difference due to trimming? It was purchased from Hobie right?

We only stock un-drilled blades as there are so many different uses of the same blade.

Simple solution? Take the opposite blade off andf use it as a drill guide. You can also download a little paper tenplate from out support area: http://www.hobiecat.com/support/pdfs/rudderdrill.pdf

These blades are Nylon and drill easily.