There were 2 versions of the 21, one with an 8.5 beam, and the (I think) Grand Prix version with a 10 ft beam. I had the 8.5 beam, this is the one Jake and Sailed in 2002. Heres the skinny:
I loved the 5.o and the 5.7, so I thought it natural to het the 6.0 or 6.1 whatever it was as it should be a monster.
I found it to be WAY overpowered even in light air, although a new sailplan would better stabilize it as the jib was like a 135 genny, way, way, too big for upwind sailing. It had the same mast as the NACRA 6.0 and an older version of a Sq top with kinda a rounded top that extened over the top of the mast. Way too much sail area again unless you are sailing with 3 people.
The boat was very fast slightly off wind and downwind(not too many spins in those days), but in big seas we couldnt tack the boat, as Jake said it had way too much depth in the hulls, they were almost waist high standing beside the boat on shore.
Overall a new sailplan would have helped, but unless you are on a lake with no waves, tacking is an issue.
And BTW, Hans is a hero, he had a lot to do with the boats we sail today, same as (dont throw rocks at me) Bill Roberts. These 2 guys were the Melvin and Morelli's of their day, and both still have great ideas, and both are accomplished cat sailors.
Hans goes a step further with his humanitariaism with his Morningstar Fisherman mission. He goes into 3rd world countries and sets up fish farms so locals can eat, and teaches them to sustain it so there is a protein source for generations to come.