If that wasn't a loaded question coming from an ARC21 owner! (boards are in front of the main beam - "shared lift" with the rudders is the interesting idea proposed by Mr. Bill Roberts).

I can't imagine that forward mounted daggerboards help the boat tack quickly but the idea of the board and the rudder sharing the lift of the sails is an "out of the box" idea...Looking at the latest trends in F18, the boards keep getting further and further back.