Weapon construction (small weapons)

Ok first (of what I'm sure will be many!) questions.  I was looking at the rules and thought the warrior monk would be a decent profession to try.  That means 2 fists (short weapons).  So looking at the weapon construction rules, it says short weapons are 12"-18" long.  That made sense, until I saw the recommended construction stuff.  I drew out what I think the maximum length should be, which seemed kind of off.  Then I figured on the other end, shortest. 

The problem I'm seeing is the reccomended pommel is 6" long total.  2" open cell foam, 4" of pipe foam.  Then the grip is 4".  That leaves a total of a maximum of 8" , and a minimum of 2" for the actual blade.  Seems kind of difficult to wield  ;D  Even worse is trying to construct it, since the end 2" has to be open celled foam, and then there is no pipe foam to attach it to even.

That being said, what is the required?  I'd guess something more like 2" open cell, 2" closed cell for the pommel, but even so, that means the blade is still on the minimum side only 4" long.