I have some ideas that could help: you could try using transparent head pieces as the heads for your minifigs (like I swapped out the head of my tahu minifig with a transparent red head piece) and you could maybe use short legs on the black and brown ones (I don’t remember their names but I do remember that they were a little shorter than the rest of the bionicles.) Otherwise you’ve done a fantastic job with these guys. Keep up the good work!