You don't want to know.
I'm still interested in this eight foot, twenty pound metal staff. That seems kind of light to me. I know of course you could make an eight foot staff any weight you want just by changing its thickness, but given that we're apparently talking about straight iron and not steel it would have to be a certain minimum thickness to remain straight with heavy use, right? It can't do you much good to be fighting with an iron pole one second and an iron arc the next and an iron S a minute after that. I wonder if it wasn't originally an iron-shod staff that turned into a giant iron staff after hundreds of retellings.
Maybe I'm just thinking too hard. My experience with iron poles is limited to the Spear of Benkei: http://i5.photobucket.com/albums/y16...zu-dera007.jpg If you're strong enough to hit somebody that weapon you didn't need a weapon.
Some large weapons - Odachi etc. - look impractical but they served to take riders off their horses or the legs off the horse. And metal shod weapons could break sword blades easily. Something heavy enough to break the bindings on Asian style llamelar armor...
Odachi is also called Nodachi..
Think Sephiroth from FF7. (yes I know people call his sword a 'Masamune' but that is both ridiculous and retarded, as Masamune Date was a sword smith, not a sword style, this is a common error in JRPG's)
It's a giant two handed katana. smaller than zanbatou, but larger than tachi.