Has anyone tried this out yet?

I was thinking of doing this homemade style. I would use a couple of layers of aluminium to match the width of this (For example.), then drill the hole for the diff. bearing in a couple of the layers, and another larger hole in the remaining layers for it to stay.

Making 2 different sized holes in a single piece of aluminium is difficult, and I don't have the tools to do that. The 2nd hole in the diff. mount is to prevent any movement, right?