my hat cc's floating (+ lots of curious)

Hi 100dou, is the project you're working on a hat? If so, you don't really need to transfer weights. The hat item you're showing will work just fine if you assign the weight 100% to the head. Since the assignment, in this case, is so straightforward, going to the trouble of transferring weight is unnecessary. Also, if you import a CAS mesh into the package with white vertex paint (Blender's default vertex color), Studio will change it to 007F00 automatically. If your hat is using Blender's default vertex color (white), then you should be able to just import it into the package as-is - Studio will put the right color on it for you. Please note, this feature is only useful for things such as hats or accessories. CAS items that require more complex vertex paint (garments) should not be managed this way.