I thought about that. But since most referances show that the inner rectangle is raised to the same height as the outer diamond, here's plan B. (Always have a Plan B!)
I'm going to cut two new diamond pieces. On one, I'm going to cut out the rectangle, then attach the second piece behind it. Last I'm going to cut out another rectangle shape, slightly smaller in size than the hole, and attach that inside the hole to that back piece. This should give me the look I want. What do you think?