What is the deepest speaker that will fit in the front door of a SCrew?

I know that 2 1/2" is the recommended top-mount depth but I want to try a set of components with a 3" depth. I also realize that I will have to make an adapter plate, but I am wondering how much room I have from the front of the speaker to the door panel and how thick the adapter plate should be. I'm thinking 3/4" MDF for the adapter to give me a little play room. This will be a component midrange with very little front protrusion.

Any ideas or suggestions?