OK, took 30 mins last night and finished this project! Like user bubi73, I inverted the back clip so that the camera can see through the mount. (different than the OP's pic).
some lessons learned:
1. I accidentally put the epoxy on the 'bridge' area that goes right below the hole. that area is over a whole and won't stick on anything. oops. I had to put black electrical tape there on the inside to make sure that the sticky epoxy stuff won't be an issue. I hope it dries up fully soon.
2. I think instead of epoxy, crazy glue can work. epoxy seems unnecessarily messy, even through it's really strong. I might try another one to test.
3. When drilling to take off the belt clip of the holster, it's a good idea to drill and lean the bit to the sides to weaken that center and allow for easy removal. Don't drill down into the holster.
Phone: Nexus 5 on T-Mobile
ROM: Purity ROM