Swap gearboxes into a tank I know won't work so I can make you a video? You don't ask much, do ya? I have no need to make such a video, I've known the steel 5:1 won't work in a heavy tank since they were prototypes. I'm not responsible for any review that says you can use these in a heavy tank, I've always said exactly the opposite. If they aren't what you want I suggest you try to return them. You did pay with paypal. right?