I remember someone saying a couple months ago(around pg30 (+/-5pages) on here) that they we trying to design a 3d printed one. But I never saw any confirmation of it being finished or uploaded here.it is not a problem but the vents can be improved (more or bigger holes). so adding a filter on the side panel will probably hamper it more
I would recommend 2x120mm fans since I am not sure if 2x140mm is supported.
Btw, any one here have designed or crafted a tophat that can accommodate 120x25 fans?