The Mutalisk crashes the editor for me (v1.28).
Also, if you do make further changes to it, could you add attachment points for the head, chest, and hands? I tried to add them myself, but could not test how well they worked in-game due to the aforementioned crash.
The Mantaling and Omegalisk do not crash, so this is only an issue with certain models in the pack. (Only the Mutalisk, from what I've tested so far.)