Hi Justin,
You need to make certain that your CBU is well attached to your studding but after that there it's really a size limit for walls. We don't like to recommend larger tiles on ceilings but I've set stone of the size you are suggesting onto properly prepared lids and not yet heard of any problems. ("Man dead in shower,... news at Eleven"

). With larger stones, you will need to take greater care to plumb your walls as even a minor diviation will be noticeable. Take your time and you should be fine with the larger tile all the way up the wall, if you like.
Shaughnn