Most folks completely forget insulation - where's it gonna be? If it's on the outside, now you need to show us how you're going to clad/roof the house. Most folks want inside insulation. That's nice. Show us that the heights are going to be compliant once you install the required R26 on floor and ceiling. (Hint: that's five inches of foam, plus at least half an inch of something covering said foam, which means you've lopped off 11" off the floor to ceiling height. Want two containers side-by-each? OK. How are you going to deal with the thermal break? Now you're cutting more width to add insulation on all sides, to account for doors and things. And if you're joining two of them side by side, now you've got a water-shedding issue. Better show that detail. And since you probably can't meet that requirement easily, that may require specialized design and/or installation.