So how big is Sion supposed to be exactly?

Or maybe a better question would be how small is Galio supposed to be, because Sion and Galio being rivals across decades of time seems a little off. And it is not a piece of lore they decided to abandon, because both Sion and Galio have taunts for each other. If Sion is let's say, a few feet taller than the average person he'd only be like nine or ten feet tall. Galio is supposedly massive. So how exactly does this lore piece make sense, given the size difference between them now?

I'm not knocking the idea of the two being the only things able to survive long enough to see each other over and over again, I think it'd be amazing to read a piece of lore where they fight. But I don't think it'd be very interesting if Sion is ten feet tall and Galio's the size of a large house.