I use a PH1 screwdriver, but have the feeling this is not the right one.
For the Pan Tilt servo part of it you will likely need a very small Philips screwdriver. The screws that go into the servo splines are really small Philips head screws. You might need a PH0 for those? I haven’t messed with mine in a long time and don’t remember what screwdriver I used.
The hat itself just uses the stock M 2.5 screws and standoffs. I use a PH1 for those.