i would send your 23.98 project to AE as 23.98 and then add gfx and cc and export back to FCP as 23.98. then add pull-down in Compressor and output as 29.97.
we get lots of DG material edited in 23.98 and we have to add pull-down in Compressor to bring it to 29.97 for broadcast. if you dont you will get repeated frames. in a lot of cases you wont notice the repeated frames but you will if you have fast horizontal motion. there is a droplet available to use in Compressor. i think you can find it if you do a forum search. or you can buy Nattress Film Converter and apply pull-down in your time line.