It’s not really ‘right’ or ‘wrong’ it’s under a fixed set of assumptions. You raise a valid point. What does happen to the top and the bottom? I was ignoring them considering only the sides in the two most extreme cases.
If I understand your case when the can is flatted the area gets much larger and when it gets taller it shrinks to a pin point. An equally valid approach
I want to congratulate everyone. I may have missed it, but I didn’t see a single person say Org Mode. Personally, I would suggest
Org ModeJoplin