here's the link to the old parts pdf

http://nacra.us/nacra/Nacra%20Parts%20(older).pdf

and here are the lines for rudder blades

4528 Rudder Blade (Short) 5.2/5.5/5.8/6.0/18SQ
4517 Rudder Blade (Long) 5.0/5.7

so it looks like the designers of the boardless boats traded some the reduced drag, gained by not having daggers, for longer rudders, to reduce side slip when going upwind

just measured my 5.2 rudders to be 805mm at their longest point

anyone got/get a measurement for 5.0 or 5.7 rudders?

azcat, it looks as if your rudders not at least 805mm long that that may be why you've been struggling to get upwind with the boarded boats