CSC lists the Tour Pak as an available option, and claim almost twice the capacity of their competitor's trunks. 6.2 cu feet seems correct to me...
I believe CSC offers the tourpac as a viable option for those triking a CrossRoads or a Cross Country. Salty's bike, I believe, was a Cross Country.
Since my bike started out as a Cross Country Tour, it already had Victory's tourpac on it when CSC added the trike kit.
I also believe, from looking at all three trikes, that CSC has the largest trunk.