Yeah, forgot about that. In general lighter weight means that you WILL get drunk faster... Still, ponies(FiM) IN GENERAL are stronger than humans. Unicorns seem to not be as athletic as pegasi OR earth ponies, let alone an extreme book worm like Twily. Still have you ever heard of a human surviving an anvil OR a piano on the head? Twilight survived BOTH, as well as some more stuff. I think there as also a cart with haybales? Can't remember. But my point still stands, that they likely can handle their stuff, if they do drink.