Yeah, it's not gonna be a problem.. Autos flower no matter how many hours of light you give them, so both plants can grow with the same amount of hours.
- Even if you want to set the photo to flower before the auto is done,it won't be a problem.. The auto will probably give a slightly lesser yield from a 12/12 period than 18/6 or 20/4, but it'll still finish up no problem.