I had a thought about that, I don't remember where I posted it though.
The idea was this; If someone were to screen print an image of the calc. piece on a bit of material similar to speaker cloth, ( for breathability ) you could have ventilation and some accuracy. As for fans, when I install mine, there will be at least one drawing air in, and one blowing it out, preferably, the blower type of fan. The CPU type mounted inside may be ok, but my opinion is that they are just recirculating the stale air.