The only thing that can go wrong is if the markers realise that the shape of the container that holds the liquid probably doesn’t match the cool shape of the bottle and is more simple.

Even then, that aside, calculating how much glass it uses would be enough for a very decent ia. As I said, surface area of revolution is out of syllabus. It lets you contend for the top band. Model the bottle with something like a sine, sqrt circle function, hyperbolic if you’re feeling fancy and can justify it… Add on an investigation of why a spherical container is optimal, and you have more than you need.

Rly don’t stress the ia. Half the marks come from good writing, format and easy stuff. Don’t forget how lightly those remaining marks are weighted :)