That remind me a chanter for wich I was trying to make a reed . It was impossible to improve the back D . I had tried all the things I know . I called Alain F. and he told me to insert a very little rush of about 3 cm long between the reed and the chanter ( in the throat ) . It was like a miracle : the hard D was there and all the chanter was in tune .
Evidently , it's not a general rule , but for "that" chanter it was the good way !