Never, i always run paper filters. I saw a test done some time ago that showed the performance of paper filter vs the fabric style. and the only time the paper restricts flow is when your trying to push through 60,000cfm or more.
or some crazy number like that, i cant recall at this time.
Just wait a few weeks boys. once all these companies get their Slingshots parts will be flowing. Don't go jumping into anything. There will be Slingshot spec parts on the market very soon. I like many others will be making some very cool stuff.