I agree with Bouke.
But if you still want to do it by your own don’t use any of the text generators supplied with the Final Cut Pro installation. Bouke has done one which comes for free with the demo of his subtitling app, I’ve done a free one as well (TextUp) and there are commercial ones both from Digital Heaven and me. All of these are created with the ‘subtitling’ in mind and will free you from the burden to position the lines for each subtitle.
The other point is if it’s a DVD you probably want to load those titles into DVD Studio – if you want switchable subtitles rather than burned in.
There are also packages which can read the FCP subtitles and convert them into a format DVD SP can read. One of them is my TitleExchange which can do the job for you. The limited free version allows to convert 50 titles a time, but you can do it several times and merge the stuff in TextEdit.
Andreas
Spherico
https://www.spherico.com/filmtools