The purpose of the foam is to protect the tank, it is not to level the tank. I am not an expert by no means and the guys here on the MCA know much more than I. So when I see their set ups and ask why they are doing something, I usually heed to their experience and follow their advice....
I have learned so much since joining the MCA so I must defer to their knowledge of why you should do something...I just say thank you for being kind enough to share their knowledge...