The stock fan in this power supply is very quiet and puts out plenty of air. It will stay till it gets noisy, then another NMB will go in. The pattern of holes in back is covered with clear tape, magic marker lines just to photograph better. Front of case cut out with foam cemented to prevent warm case air from recirculating. Foam is cut, stacked, and glued to the shape of the case front.
Front hole made with aviation snips, it's a little rough, but it's covered by case front.
With the rear I tried a saber saw with a metal cutting blade. Since I didn't want anything else to break from the vibration, I switched to a Dremel tool with an abrasive disk. I don't what they are called elsewhere, but I buy them from dental supply houses as Separating Disks. It cut the metal like butter, so that will become the tool of choice for other cases. The down side of the Separating disk is the amount of very fine metal dust it produces.