Well, a day after I posted an updated picture -- I added a new more streamlined upper grill block for my xA:
It projects forward to the "nose" of the bumper, and smooths things out, and increases the angles to (hopefully) better deflect the air flow around the car.
I need to make it more symmetrical, and trim it, so it doesn't "want" to lift the lower outside corners...but the air will be pressing this into the car, so it will suffice for the moment. And later as the weather warms, I'll adjust the lower opening for the right amount of cooling.