Raulston is only a recent re-discovery - irs one of those forts we knew about in 1850, then forgot about, the site is now a glider club, EH announced its "discovery" a few years back.

Prior to then Hambleton was the largest IA Hill Fort but Stanwick of course is much larger at 500 agres, but because its not on a hill it doesnt seem to count.

Personally, when I'm worrying about fotified structures I'm looking for those forts that might hold the most warriors, have possible strategic links etc. I think the fact that a fort may be on a hill makes no difference whatsoever.