No worries, David. Welcome to the "Dafia".
Two-handed use is certainly an option and I'm sure it was utilized from time to time. However, the longer handled forms are typically gripped closer to the guard (blade/handle junction when a guard isn't present) in one hand. As you note, this causes the center of balance to shift back towards the guard creating a light, quick "feeling" sword. The long handle thereby acts as a counterweight to the blade, much as large, heavy pommels on western medieval swords did.
For some more information on the handling characteristics of dha, check out the HOS article here:
http://www.arscives.com/historysteel...ea.article.htm
Best,
Andrew