As a symphony harpist with many students, I have seen a lot of hand
positions. The main thing is whether a straight or curved finger works well for
your student. Every hand is a different size and shape, and it will only cause
frustration if one tries to pound a square peg into a round hole. I learned the
Salzedo method, but I have made some adaptations to compensate for a
rather short 4th finger and long 3rd finger, You can imagine the buzzing this
would cause if my 4th finger were completely curved. So it only curves on one
joint! Also, in big stretches, I have to flatten my 3rd finger if I want to place that
4th finger. The height of the thumb can make it easier for the 4th finger, as
well. Try lowering it a bit and see if that helps. It does not have to be too high;
in fact, it should not be so high that it shows pulling across the palm. It should
just sit comfortably where it is placed naturally, with no stretching. I hope this
helps! As for glissandi, you play the next note with the thumb coming down. (I
hope I understood your question.) Also, watch their elbows! If they are
drooping too far, the best hand position in the world won’t work.