The Denver Post article about it here... U.S. Whitewater Rafting Team just misses speed record down Grand Canyon in custom-built cataraft
... said that after a close call in House Rock, they switched the rear most seats around and had those guys facing down stream presumably so they could see and react to things better. They also had a guy on a "tiller" to steer it. I'm sure it was still a beast to maneuver though.
My high school had a crew team and I was on it for a few years and I know the oars that they were using are designed to row one direction. I'm sure they could get some power the other direction, but not nearly as much as the correct direction.
They may not be as big and burly as Hance and Crystal, but I think the two rapids I'd be most nervous in with a boat that size is House Rock and Bedrock. Tight squeezes and a 50 foot long boat sounds hard to me. Watched a couple of J-rigs do Bedrock on my last trip and it took some deft maneuvering at the wheel.