1. Download Quicktime Player 7
2. Export your video from final cut in It's default settings.
3. Open your video with Quicktime Player 7: Go File, export, choose Movie to MPEG- 4 in the drop down menu, then click options, choose the video format H.264 and change the dimensions to 720 x 720, click ok, click save.
You have a square video!
Now use dropbox to get it to your phone.