I realize this post is a couple years old, but it still comes up when I search for the problem. As an update, I just output a 720p sequence from Final Cut through a Blackmagic HD Extreme cross converted to 1080i to a Sony HDCAM deck.
The trick is to use the 720p 59.94 easy set up… if you use the 23.978 you get crazy artifacts on the cross convert. There’s also about a two frame lag so do a test and adjust your in point on layoff accordingly.
But again… a blackmagic card will do it… given you have the right settings.