Has anyone else done this. H264 seems like an odd choice to me. Is it a simple case of just exporting this from FCP and changing the size to 2048x1080? I've never had to do this before so just want to make sure I have got it right.
30Mbps H264 will yield good quality at that size.
Resize it with Compressor.
Going from 1920x1080 to 2048x1080 will be some distortion, but won't be much noticeable.
To keep the original aspect ratio, the picture should be 2048x1152, so you can adjust the picture on the Geometry tab.