I've been experimenting with this, too, on a variety of items. For mysterious reasons some work great, others decide they need to shrink themselves to extremes, and yet others become incredibly loose (like scale 200% or worse!).

By accident, I found a solution. The critical thing is immediately after running the DynCreator save the item as a Dynamic Cloth Asset, then delete if from the scene, then re-add it from your saved file. As long as you do that, when you drape it will respect the geometry properly. If you don't, it seems to be utterly confused about the "rest" position.

A second workflow thing...

If I start with a clothing item that is a conforming one, then convert it to a prop, sometimes the object will simply refuse to react to the DynCreator script. If you export that item as an obj file (format doesn't seem to matter...I use Blender), delete it from the scene, then re-import your saved obj, the script works fine (although after running the script you have to save it as the Dynamic Cloth Asset first, then delete, then load your saved one). Often you need to do this export step to clean up/connect parts anyway so it's not that big an issue.

Perhaps not the most efficient workflow, but at least it works.