Staff strikeing surface

[Harbainian]

In the book of war it says that a staff must have a minimum of at least 18 inches of strikeing surface on each end. My question is, If you have a stabbing tip on both ends, does that count as part of the 18 inches, or is it 18 inches, + stabbing tip. Also is there a max handle length on staves? Is it the 18 inches or 1/3rd overall length like normal weapons, or it is special like glaives.