Router adapter for large inlay

I was creating an inlay of a Star of Black Walnut onto my Red Cedar deck about 2 feet across. My router would not lower the bit enough to use wood as a large guide.

So I used 2 strips of aluminum bar which I drilled and mounted in place of the router base. The base and the bars were about the same thickness.

Careful to not go outside the lines, it worked great. For freehand routing of larger areas, I could not think of anything better.

Now, if it absolutely needs to be be flat, I would recommend steel or iron for the bars. The aluminum has a little flex, but not enough to cause problems with the inlay.