Use FCP's Export - Using QuickTime Conversion and pick a compressed codec like MPEG-4 or Sorenson 3. Then experiment with various frame sizes and data rates (video
and audio) to end up with the size you want. Video at 320x240 frame size and 600-1000kbps, with audio at 64kbps, 44.1kHz, Mono should do the trick. Bear in mind, though, that PCs tend to be a lot less tricked out with QuickTime components and you may have to accommodate, or use Flip4Mac make a WMV for PC users.
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