CMS 3 Column Grid Layout --> 2 Outer Sidebars @ 15% + 1 Inside Main Column @ 70%
 

My default 3 Column Fixed-Liquid-Fixed grid is messed up and does not fill 100% of the width. It seems to go only 80% wide. Not sure if its a bug.

I am hoping someone can help me create a grid layout that has a sidebar on both sides and one interior column with the proportions being something like 15-70-15. Is there a way to manually size each column?