It'a kind of hard without being there and seeing it, or having a diagram. If it is not done properly, you won't get good airflow in each room. The ducts need the proper sizes and deflectors based on the room size and heating/cooling needs. WV climate ranges from quite hot and humid to moderate in the mountains, so there's no easy way without more info to know what your loads and needs really are. It doesn't sound like what's there is particularly efficient. Often, the best way is one central trunk with branches off of it where the main trunk gets smaller as it reaches the end. This often can provide the most even airflow, but not knowing the sizes, distances, etc...it's all a guess. You want something better than a guess. Post a drawing of what you have with some dimensions, and you'll have a better chance. But, keep in mind, a designer gets paid a fair amount to actually crunch the numbers and do this right. That may limit how good an answer you get here for free, but you never know.