tuning and ruining reeds

[Vadimonium@xxxxxxx]

hi, 
i want to tune a Bb harp's draw three down a whole step. i've gone thru 
several because the reed gets ruined as there seems to be so much metal that needs 
to be removed to tune a full step. any advice as to how to have the reed 
retuned a whole step - like, a down to g - and not destroy the reed in the process?
thanks,
vadie