Actually according to the reading I've been doing all day to nay say all you poo poo-er's that is not the reason barrels are shaped that way...And actually it is MUCH easier to just make a box, than it is to make a barrell...that's why Coopering is a specialized trade, while box building isn't.
It was simply to make moving heavy things, whether it was beer, or nails or flour
easier to move.
They are losing their importance in other than the booze making industry, because there are other more efficient way to dong things, they don't need to be rolled anymore. And I betcha had they had a way to easily move Square liquid holding containers back in the day, we wouldn't be having this discussion, it would be the norm.
Heck, if the OP had simply come on with an already finished version of this, instead of asking for help, we'd all be humping his leg. That's the funny thing abut this place whenever anyone comes on looking for help with something that may be a little (excuse the pun) out of the box
People come out of the woodwork to tell him what's wrong with his idea, instead of trying to help him solve any technical hurdles....
Bubbles, I hope you try this out, if anything to put the naysayers to rest. Or to prove to yourself if this isn't feasable, not just take these folks word for it.