Hi,
the question wasn’t directed at me, but I would put a 3 mm coil in it and pull the Cotton Clouds into it. That should work well. 
Or perhaps is the 5 mm meant to be 2 x 2.5 mm coils? Because then you could use the cotton by taking minimal amounts from it - if at all - in case of double coils. Because as it is, you are thinking correctly, the Cotton Clouds is marked as 3