I'll try and post some pics later on today, I'm happy to hear you had a similar situation, I would honestly love it if it the flagtail grew fast, the dat isn't attacking the flagtail anymore buy I can tell the flagtail is still afraid of the dat lolGood choice, that's exactly how my NTT & (1" bigger) Flagtail started out: NTT showed him who was boss for about an hour but since then they've been good friends (even if the Dat does try to steal food from the FT lol). Though the NTT is about 5-6" now, sometimes he's shy to come out and feed until he sees the FT eating first.
They should do well together (though the FT will grow a lot faster), post some pix when you can.