The case this thing is derived from (thing:25612) was not printing well for my .35 mm nozzle and slic3r (hollow, weak walls). I have made the walls 3 mm thick, added additional lip to the top of the case, and placed support legs under the lip for clean printing. and successfully fit to an iPhone 4.
This is working well for me, I hope it helps out my Open Source Hardware friends as well.