I have a pair of 9'6" cataracs. Im not sure how you would go about balancing them. Personally I think you shouldnt need to balance them. Im kinda small in stature, I dont have a problem with fatigue after a long day on the water. I found that if I get my oar handles as close together as possible while rowing, it is a lot easier.
One thing I dont like about mt cataracs is the blade. The blade is so wide that sometimes while in really fast water it is hard to pull the blade out of the water. If you run a lot of white water you may consider buying a pair of Sawyer wood replacement blades. The are a lot slimmer.
Good luck and enjoy your new boat.