Dottie,
I was told not to do any waterfowl with other types of birds. The person that told me this said that ducks need higher humidity. Now, the books say that ducks and chickens take the same, as far as humidity and temperature.
Whether you are laying the eggs on their sides, or standing them upright in a carton/turner, they need to be about the same height. If they are different heights, in a still air, the higher eggs would be hotter than needed, and the lower ones would be colder.
If they are about the same size, I would say it's up to you, but like I said, I was told to do ducks by themselves.