Whoa, that was fast, Mike.
But it looks like we've forgotten to put one little aspect of this process into the FAQ, and that's FCP's own Make Freeze Frame command.
To make it not "convulse", apply a De-Interlace filter and try both the de-interlace and Flicker Filter options. If you want to go the route of exporting an actual still image file, export a TIFF or a TGA, not a JPEG.
And when you're editing, you should not be relying on the Canvas to judge the effect. Hook up an external monitor, even if it's just a TV set -- FCP's Canvas not only shows effects in a degraded form, it also doesn't show any sort of field- and interlacing-issues. So if you keep going like that, you'll end up wasting a lot of time and blank DVDs while those issues still persist.
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