Not sure if it's still the same in newer versions, but in P6 you can convert a prop into a figure very quickly.

In P6 all you do is load the prop hair into an empty scene, then select 'setup', you'll get a warning about opening a prop in the setup room and another if there are morphs in the prop, click yes on both, once it's loaded into the setup room just go back to 'Pose', you'll get another warning (click yes again). You now have a figure in the scene rather than a prop, now it's just a case of saving it back to the Figure Library.

The resulting .cr2 does work with Auto-fit as I've just tried it ;)