Tony/Rich - I purchased both the aluminum and steel version of that mesh - go with the steel. The aluminum is somewhat flimsy and doesn’t hold its shape very well. I made the grate for my radiator exit out of the aluminum and after driving around for a while the wind/vibration/whatever caused the aluminum panel to distort slightly. It was enough to annoy me. The side vents are less prone to this distortion and less obvious but I went ahead and made mine out of the steel since you get so much of it when you order a piece.
Not sure what you plan to do, but I built plates that matched the openings along the side and back. The two side vents proved to not be "square" and did not match, so they are custom to each side. The cutouts in the two plates were cut the same so the appearance is symmetry. Same with the back plates. I used an aluminum grid from McMaster Carr (they have a lot to choose from), but the actual size to fit was a small area and the grid does not move. I panel bonded the aluminum to the cut outs and cleaned them up prior to painting. Just an idea for you.
I use black hexagon aluminum for the exit of my rear panel. It was rigid enough even for the larger piece, and black oxide 1/4" 12-point fasteners (pretty small head) are nearly invisible, and provides very positive locating and fastening.