I've been using this to get rid of the legend and permissions blocks. I would venture you could jigger it to fit your needs.
Code:
/* TW7S - Remove Legend and Permissions Boxes */
#usercp_content #forum_icon_legend, #wgo_legend, .forum_info .options_block_container, .thread_info .options_block_container {
display:none;}
/* TW7S - End remove Legend and Permissions Boxes */
I'm going to have to try your idea out at my place. I'm running in a 2 column format and that would tighten up the bottom of the forum page.
Edit: No joy there. Maybe the 2 column css trick is messing it up. I'll play around with it.