Add some space on top of your Hammond 1550P Box.
All you have to do is to cut 1 wall (the top) and add some magnets (6mm) and your box is ready for a mechanical or MosFet SetUp.
I use this parts that will fit perfectly in this build:
* Hammond 1550P >> http://tinyurl.com/ldotr4w
* 2x18650 >> http://goo.gl/8WMQH0
* Switch >> http://tinyurl.com/mvqem3w