I use OEM carbon and they fit fine but agree its a shaky set up.

 

I believe i'm missing a cover too.

 

I had the same experience as 32krazy, I had to crush mine in there a bit but it's not going anywhere.

I had not a rattling but a flapping, like a playing card in the spokes of a bike wheel. Somehow a 6"x4" piece of black hefty bag had made its way into the pollen filter area and was caught in the fan.