Constructing a double ended weapon
From BelegarthWiki
double ended weapons are really a rarity in belegarth there kinda hard to use but once someone masters it they're pretty reliable weapons
Cores
First your going to have to decide what kind of core you want PVC is out of the question unless you use another core inside it but that just leads to overly heavy weapons bandshoppe pole or rattan are your two safest bets band shoppe is a little heavier but cheaper and rattan has a significant amount of flex and you have to be careful because sometimes they don't always pass they are however, significantly lighter and since they really are staffs are pretty ideal for this purpose.
How to build
Materials
Core of your choice