Hi Wolfgang, and raggy,
I don't have any real scientific basis, but I've always found that a 40°-50°Leading Edge (LE) weedfin to be more "forgiving".
You don't have to be quite so precise with the pressures and angles when you have the swept back fin with more area.
Do I consider a 30° LE fin a weed fin.....?
I do know that a 30° LE is a Wolfgang Lessacher "Speed Fin" design, and has to be one of the fastest speed fin designs ever developed, especially when you put it under a board that Martin van Meurs is sailing.
But I don't think a really small fin (28 cm is small) will help raggy with his speinout problem until he learns to stay off the fin until he gets the speed up.
Then, like all tiny speed fin designs, you can hammer away on the fin.
But you have to get up to some speed where the little fin can develop enough lift to counteract a heavy rear foot.
I always just tried to "pressure" the fin a little as the speed increases, but if the fin feels
soft or kinda "mushy", I back off the pressure and gain a bit more speed and try again.
When the fin locks up solid, you can feel it, and then you can really push on even a very small fin.
Of course, on the courses that Martin sails, (i.e. beam reach and lower) you don't really need to push the fin much at all.
If you are sailing and trying to "go deep" you almost have to back off the fin pressure quite a bit to get the board to turn off the wind.
Hope this helps,