The blade of my large, Regular Sebenza is just a hair under 3.5 inches long. Thats using the AKTI standard of measuring blade length: measuring the distance from the top most part of the handle to the tip of the blade.
I dont know for sure though if all Regular Sebenzas have that same exact blade length. Mine was made in October of 2001, if thats any help.
The large Classic Sebenza that I handled in a pass-around had a slightly longer blade. It was maybe an eighth of an inch longer and therefor over the 3.5-inch limit.
You might want to post this question in the CRK forum in the Manufacturers forums here at BFC. The people there might provide better info, but I think the Classics blade is always a little bit longer than the one on the Regular.