OK, tested in Slow Poser (Poser 5) and it works just like it does in Poser 4/ProPack, except you do not need Nulls as Slow Poser has no crosstalk capability. So you can save and reload and the injected morphs still work as FBMs without problem. Which answers my own question from the last post. I guess if you mess up and forget to put Nulls in in Poser 4/ProPack and you discover that you need to edit later, you'll just have to open in Poser 5 for further editing rather than Poser 4.