Oh I'm not sure about pre-made fan filters working or not, it looks like there could be room, but the drive bay covers connect right ontop of the fan; so I myself would probably go the custom route and just get some of that black filter mesh you commony see in vacuum cleaners. It could probably be left as a big square pinched in between and covering the entire fan since the front fans have the backside to the spinning rotor facing out of the case. I myself would probably reduce filtering marginally and just cut it to fit so that it could be recessed right into the front covers. I'm a noob just trying to help ideate though, so take what i say with a grain of salt.