Hight of whirligig figures

Hi
My grandson wanted me to make a whirligig of two men sawing a log. I’ve got a general layout of whats needed and how to construct it, but I’m not sure how big the figures should be.

Is there a standard for figures, if you make them too big it will throw the model off and wont be able to find a good centre point.

Any one made any whirligigs !

Thanks a lot.

Michael
(Centurian)