BLF,

If you have hair or other items that do not quite fit your current characters might I also suggest that you read a few tutorials on a poser feature called "magnets".  Magnets are a real godsend, once you practice with them for a bit you can easily make adjustments to things like hair or clothes to fix a lot of issues like poke through, sizing, etc.

It's possible to take hair for one character, like V4, and using magnets resize and reshape it enough so that it fits V3 or other characters.   It's also possilbe to use magnets to create your own morphs for hair, clothing, and pretty much any prop or character.