Forgive me if this sounds like a stupid question.

I have a 5 year old hawg(think it's 2 litres).

Going to do an all day ride(70 miles) so want plenty of water with me. Any idea if a 3 litre reservoir would fit in a 2 litre hawg? I love my hawg so would prefer not to have to get another backpack that can hold 3 litres if my one would work.