I had problem with the two other Structure/iPhone 5 case files on Thingiverse, so I decided to give it a shot myself. This is the fusion of two STLs; my customized iPhone 5 case and the bracket file from Structure's web site. It fits my phone perfectly, holds it well, the phone is easy to remove, and the bracket seems very secure. Enjoy!
I use a 0.5mm nozzle, so this design accommodates that with fairly thick walls. I made mine with natural ABS, and when the print was complete I sanded and sealed/melted the phone side walls with ABS to aid in preventing delamination due to stress from the phone being pulled out, but it may not be necessary, especially with PLA or other materials that behave very differently from ABS.