Need box design quick (free please)

[Flexin'01]

I'm wanting to get started on my build for my new box by tommorow hopefully. This is for 2 12" L7s. I would like it tuned to 32hz. I want it to be sub back/port back, with a slot port. My specs are 42 wide, 21 tall, and 18 deep. Can someone help me out please?
Thanks

Edited*

[miker]

Tune it lower if you want to "hammer" the lows...