Calling all Poser SPN fans :0)
Aki has done a custom Cas morph.... you don't need the M4 morphs for this and it will work in both Poser and Daz studio.
I think she's got his mouth pretty much spot on. It's a great starting point for you to make your own Cas character (you just can't redistribute Aki's morphs) if you want to tweak it 'till it works for you ;-D
www.sharecg.com/v/63087/browse/21/DAZ-Studio/Castle-for-m4-base-for-DS-and-Poser Have fun !