You can massage that flange a bit with hammer and dolly. You'll want to do it a little at a time, to prevent wrinkles or changing the curvature of the cowl panel.
I did that a little on mine with a railroad dolly (has a right angle corner) and cross pein body hammer. A toe or heel dolly would likely work as well. I think a dolly would be a bit better than a piece of channel or angle, but use what fits.
The other alternative is to run a weld bead along the outside to sharpen up that bend, but that has it's drawbacks, such as possibility of burn thru, then a lot of grinding to get the profile correct.
