shippo,
When you reference "50 fps", do you happen to know if that's fields per second or frames per second? Depending on the answer to that, you may or may not need to adjust that.
When it comes to file size, you have frame rate, frame size, compression type and data transfer rate affecting the final size.
As Russ and darby have suggested, data transfer rate is the main thing to experiment with (since you're publishing for Vimeo, the other setting are pretty much locked in).
I have found that when it comes to playing with the bit rate, a video with a 1280 by 720 frame size needs between 4,000 kilobits per second and 5,000 kilobits per second to maintian good image quality. While you might get good results at a lower rate, high contrast areas in the picture are very, very, very likely to show loss of image quality.
If you need to get your video up asap, start the upload late at night. As long as your internet connection doesn't drop out (knock on wood), you file will be uploaded by the morning.
Also, (for what it's worth) is there any place close by that has fast internet that you could use? If you have access to a computer lab at a local community college, a 1GB file will probably upload in minutes rather than hours.
-Warren