The longer the reed the deeper the call will be. The shorter the reed, the higher pitched it will be. The reed also has 'dog ears' on it. The bigger the 'dog ears', the raspier the call will be.
This is what I would do:
a) Remove the current/orginal reed and mark it with a marker. You want to keep it for future reference. You know it is too high, so you want the next one to be longer.
b) Put in the new reed without cutting ANYTHING off of it. Put in the new cork and use a safety knife or razor blade to trim the excess cork from the sides. Look at the existing cork for reference. Make sure you determine the natural bend of the new reed. Put it between your thumb and index finger (either end of the reed, long ways) and press down. This will show you which way it bends by default. You'll want to place it onto the toneboard so that the natural bend will lift it UP off of the toneboard.
c) With full length reed and new cork in, blow it. Too deep? Use a pair of VERY, VERY, VERY sharp scissors and remove the SMALLEST sliver possible. Blow it again.
d) Keep repeating step C until you get the call ALMOST to the sound you like. I mean get it to the point where you think one more sliver is all you will need to get it 'there'. This might take awhile if you are removing TINY slivers each time.
e) Look at the original reed and cut 'dog ears' on either side of the reed.
That should get you there. Be prepared to waste a couple of reeds during this process. Make sure and mark each one as you do it.
Oh yeah, when you cut the cork with a safety knife, put the insert down on a hard surfe so that the bore (exit hole) is down and the tone board (reed end) is up. Cut the reed as close as you can to the insert without actually cutting into the insert. Make sure and cut DOWN so that you don't dislodge the cork from its slot.
Hope this helps....
"I'll start spending less time with my dog and more with my wife when she starts fetching ducks for me"