Exporting Settings in iMovie

Hello all,
I am trying to export movies using iMovie but am not having much success. I want to post them on the web with the dimensions of 400 x 300. When I used to use Movie Maker on a PC I could get really good looking movies that were only a couple megs per minute. Using iMovie exporting to a QT video I can’t get anything decent even at 5 mgs/min. Here is what my settings are now:

-h.263 (don’t feel like enough people can view a h.264 video yet)
-15 fps
-Keyframes every 150
-6000kbps

Anyone have any suggestions?