Thanks – this is they key:
“It seems a little odd to me though as 720×223 doesn’t seem like it could be 16:9 by any measure I can figure out.”
It’s definitely not 16:9 as I was at the stadium today and the 16:9 tvs all had the letterboxing while the same images on the jumbotron was uncropped. It looks more like a 2.3x:1 to me, so I guess I’ll have to tape up or grease pencil my monitor when I do the shoot.