The first task will be to cut a pair of top exhausts. These will be 92mm fans. Note the air powered drill. I burnt out a big 6A Makita drill making the purple case from having to run the drill too slow (so as not to kill the holesaw). This one runs with a low rpm by default and has power to spare.

I took my chances and got lucky cutting the two holes so close to each other. The metal of this case is so thin I was sure it was going to rip but the slow rpm, new saw and cutting fluid paid off.

I am going to "stealth-mount" these fans. Basically what that means is that from the outside, you will not be able to see how they are attached (as opposed to screwheads showing). So what I did here was to grind off the heads from some 8-24 machine screws and thread on a nut. The nut is to keep the machine screw sitting flush so I can glue it to the metal. Another advantage of the nut is when you are tightening the fan down you are pressing against the nut and not the panel so the glue bond is not stressed. It is glued with JB Weld and I used a fan grill to get the proper spacing for the bolts. In retrospect, I should have used an actual fan instead of the fan grill. I found the fit a bit too tight when the fan was placed (and broke a bolt off in one case).

Next is to cut out that preformed grill from the back: