So I have my school ID to get into buildings, and a lot of people have phone cases with a little slot in the back to place a card. They just put their IDs in the slot, so they can just tap their phone to unlock the door. I also know some people who just have more rubbery phone cases (TPU I'm guessing) that you can slip the ID behind the phone, and it not loosen the case up. Right now I have a hard plastic case, and trying to put my ID behind it doesn't work. Would a TPU case be flexible enough for me to put my ID in the back without messing up the fit? I know I could just get a case with the card slot, but I want a case I can get a custom image on the back of, and I've only seen that on hard plastic / TPU cases. Thanks for any tips.