twenty-eleven content container resizes when comment area removed

I have a background image I want to remain static on home page, without blog functionality. But when I remove the comment area, the image crops to half it’s height. Have combed through codex, tried various CSS code (i.e. fixed size on image, container-called ‘primary’-specifications, but nothing works. Even made a ‘snarfer’ page template to try and address this issue.) Is it a default function of some kind in wordpress? And how can I change it without affecting blog pages?

site is: http://curiousexplorersclub.com/wp/?page_id=326&preview=true

Thanks for any help! It is greatly appreciated.