Help with finishing touches of big Battery enclosure

Hi can someone help me smoothe out the surface and curve the enclosure ever so slightly maybe 10degrees so it can fit my board.

I will put the finished enclosure up on thingverse when someone can help me.

here is the STL https://drive.google.com/file/d/0BzFtBU0Jt23zM2NlVjhFUWtsN1U/view?usp=sharing