Though I do not know for sure, I think that depends. Though Kraata-Kal was just a kraata exposed to the same energy that made the bohrok into bohrok-kal and then processed into rahkshi by normal means, the only thing the "kal" energy changed was the abilities. Teridax had to modify the suit himself to make him the way he is. So, the parts Teridax put on there (like wings, a tail, etc,) may get in the way of fusion. Because of these additions, every kraata-kal could be different depending on how its suit was enginiered. Note: all information was gained from the wiki.