With my old lexan blades I experienced a lot of weather helm and occasionally odd stalling situations (I am not sure but I always suspected that those relative flexible blades bend or twisted under load and caused some erratic stalling). Later I found old EPO's or what might be original composite blades (not sure what they are) for my Hobie. In those blades the holes were placed to allow more forward rake. When I tried to mount them in my lower castings I noticed that I had to remove a good amount of aluminum from the inside of the casting so they would swing far enough forward to lock up well. It is pretty difficult to remove any stuff from that casting - power tools cannot be utilized - filing is only possible in short strokes. In other words - it took a long time.
The new (to me) composite blades fixed both the extreme weather helm and the odd stalling situations.