Think twice, cut once.
I don't have an example pic, but some air dams are just massive deflectors over the two front wheels; while other have been like what you show with a notch at the center bottom for a central jet. One, the other, or something in between? An added advantage is extrra clearance for gravel roads.
Another opportunity is on the sides where you could incorporate air curtains for the front wheels. Maybe the aluminum stands proud with an inner baffle wall terminating in a vertical slot. Stamped louvres would be cool.
For the splitter it will need to resist aerodynamic deformation. Look at the fasteners and their number for some idea.
And the thickness of the splitter. Overbuilt for your application, probably.
Does your Metro have little black wedges on the door window frames? Mine has one on the right [I just noticed], which lead me to two holes one the left frame 3/4" apart in exactly the right location for a peep mirror. With the convex inside mirror and two 2-3" outside mirrors I could remove the big, honking thing that won't fold back.
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How are the pizza pans doing?