I not would expect animal models to match up to clinical (meaning human) results - unless the studies were done with rhesus macaques - a ' lab' species that shares a GLO mutation with primates, so they have a dependence on dietary vitamin C similar to humans. The only studies I could find were with guinea pigs - which makes as much sense as testing cholesterol intake on rabbits (which, yes, is where we get "cholesterol is bad")

That 2008 study suggests that the MDR (currently 90mg/day) is too low (if you classify oxidative stress as a deficiency disease) - but it's not clear that anything in excess of 1g/day provides any benefit.

Contrawise, there's no evidence of taking up to 16g/day causes any harm. (I'm using 16g as Linus Pauling self-reported taking that amount without ill effect).