I rarely crack reeds. Here's what I do..Soak GSP cane for 20 minutes in hot tap water. then I use a 24 teeth/inch hacksaw blade to score the tube from about 1/2 way between 1st and 2nd wire locations to the butt. Bevel tube from 2nd wire to butt. Wrap tightly with twine from mid blade to butt..then insert forming mandrel to open butt, then remove forming mandrel and insert short mandrel to prescribed line. Remove a few wraps of twine from the butt and place 3 turns of 21 ga wire and tighten moderately, then remove a few more wraps of twine, place 2 turns of 22 ga wire approximately where you want second wire and tighten moderately, then remove remaining twine and place 2 turns of 22 ga wire for 1st wire. tighten moderately, then move 2nd wire to exact location (I use the thickness of a certain pair of pliers to measure between 1st and 2nd wire. Then aggressively knead or mash the tube from the second wire to the butt and tighten all wires quite tightly (a bit looser for wire #1) and place on mandrel tips for several weeks of drying and settling. After about 2 days of resting on mandrel tips I retighten all wires.. 1st wire moderately snug, wires 2 and 3 quite tight. I usually apply wrapping (hot glue for me) after about a week of drying.
This proceedure works fine for me...any cracks are small and do not extend more than a few mms into blade.
Hope this might be helpful to you..
Greenville (SC) Symphony