@DFAThat's something you'll have to find out
Edit: Also, it's not assumed that you'll reach the full height of the champion you embody. Let's say you embody someone tall like Zac, you'll probably grow harshly different then someone that embodies Shen or otherwise. If all our characters were the same height, some would grow a few inches to a foot while others might reduce in size. Also, it depends on your creativity. Notice that a wall should normally stop Sion in his tracks, but he broke through the one created by Yorick (who usually doesn't have any terra-forming abilities). It's alright to customize your characters abilities and design somewhat.
Now if Yorick begins teleporting around or begins throwing fireballs- then we might have a problem.