The fan definitely blows out in the original configuration. The filter protects the fan, the air you breath and somewhat restricts airflow. Some feel the original filter changes air flow restriction as it becomes dirty and opt for a more consistent filter material. No filter would require a change in profile (as would different filtering materials), but it can be done if the opening where the filter holder is inserted is closed off. As far as filter materials go, besides metal mesh, some have used green scotch brite pads (with and without holders) to replace the filters with good results. I'd be concerned that paper towels might be too restrictive and prevent the fan from drawing air through the roasting chamber. Also, whatever material you use, it needs to be a fairly tight fit or the fan will just draw in air through the top of the filter holder opening.