Think I should ovalize the flat plate or keep it rectangle? If oval, I would go somewhere around the water pan's bottom footprint. Yes with foil, I could simply create a very shallow wall around the edge.
Kurt, I see your deflector is below the water pan and Bear, yours is above. Hmmmmmmm
I would keep it oval.
I like mine like I have it, because I have the prop inside the water pan that I use to raise & lower the left side of the deflector plate. That's how I balance the heat out from left to right (in my Gen #1).