How to edit 15 fps footage in Premiere Pro without upconverting

I've got a 15 fps Quicktime video shot with a digital still camera, which I want to edit and post to the web. When I try importing it into Premiere Pro, it gets automatically converted to 30 fps, which makes it terribly blurry. Is there a way to force Premiere Pro to edit the clip directly in 15 fps? I've looked for a way to change the frame rate in the project settings, but it only gives me four or five standard options, and no 15 fps.

All I want to do with the final video is to post it to YouTube, so the 15 fps @320/240 resolution is acceptable, but of course I want to avoid any needless blurring.

Thanks for any suggestions.