Using Toast and Viddler

I've got a number of TiVo recordings that I want to archive. Right now they are in the .tivo file format and I've used Toast to edit the recordings. I'm experimenting with exporting those files now and I'm using Toast to encode the videos for Apple TV. Toast will only allow for a max resolution of 480 which is fine with me. I selected "high" quality, but I don't know if that'll make a difference. I notice that the estimated file size is over 1 GB with a playback at over 2 Mbps (I think). I'm curious if the file will really be that big. Does the bitrate increase as the resolution decreases? I kind of doubt it. I need the files under 500 MB because they'll just take up too much storage space. So, that's what I'm testing and will just have to see how this ends up. I'll probably re-encode in Toast if the file is too large.