ducts are a very bad idea, you need to let the fans do their job. you just cant really predict and control your computers air flow, i mean its really by chance and ducts could have an adverse affect
you can buy 80mm drill bits from bunnings (i'd know i work there) for about $10 you get a pack ranging from 10mm to 120mm that go through metal, use a corded drill and make sure too place masking tape around the template of your 80mm hole to stop the paint flaking and metal protuding outwards, drill slow if its aluminium you dont want too tear up the metal
you'll also need to drill 4 holes to hold up the fan, its very tricky and annoying but if you got alot of time it can be done well, try not too fuck up holes because if its like 5mm off you cant drill another hole it'll just make it bigger so you need to make it perfect
make sure your case is in a well ventilated area, not in the corner of your desk, but on your table, sometimes near a window is a great idea
just little shit like adds up
