About the only way a homebuilder could effectively make a long dagger without a mold would be to get a machined wood core and lay up carbon on the outside. Even this keeping a fair and constant section is the work of only the most skilled pattern makers and finishers.

I went out with Matt when they were testing the long daggers for use on the F16. They purposely used the same chord length on the boards so it was possible to interchange them and better test varying lengths and foil sections. The one thing about the longer boards was that it made it obvious that board height was a critical setting for performance. Too much board in the water and your vmg went to crap. The board height position is near as important as mast rotation. (very bad deal IMO for beginner and or even moderate skill level crews as now there is even more to do to sail) The long ones did help getting the boat to power up in the transitional speed winds. Once you were moving, you were quickly pulling up some as the wind built. Once double trapping it took nothing to have them up at the same depth as the normal high aspect foils, but now you have the dagger sticking up on your hull all the time, in the way for going in and out and moving crew weight. Never mind the danger of the sharp trailing edge meat slicer way up in the air just waiting to catch the crew sliding forward if you happen to stuff it.