You must convert the footage with the Panasonic Frame rate converter plug-in. It is found in the Extras folder on your FCP 5.1 distribution disk. Drag into the Plug Ins folder and restart FCP. Highlight the clip in the browser, go to Tools -> Frame Rate Converter, select the target fps rate and then a destination for the new clip. Import the new clip back into FCP. Note, you will not have audio with VFR clips. That's all there is to it.