Hi, izzywheatley!
The screws at the bottom of this generation iPhone (and all iPhones these days) are a pair of Pentalobe P2 screws. I would agree that these are definitely two small to drill out without risking damaging other internal components.
I found another iFixit forum about a similar situation on an iPhone 6 which uses the same screws as your phone. How can I remove a striped pentalobe screw?
A user named Mayer posted this link on that forum to a video that might be helpful.
https://www.youtube.com/watch?v=YXGlQdAW...
In my experience the other thing that can sometimes help is to get a strong small magnet and attempt to pull the screw out the tiniest bit then get your fingernail between the head of the screw and the phone. If you can manage that try spinning the screw any way you can (potentially like demonstrated in the video by using a flat head screw driver) while levering up on the screw.
I hope you have some success!
Milo Firestar
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