Thanks all for the comments.
ozpiper, I bend all my stems with a heat gun and slowly working my way along until I achieve the bend I want. At each stage, with my fingers holding the hot stem (ouch) where I want it, I then plunge it (while still holding it) into a bucket of ice water. It doesn't need or require a lot of ice. A dozen or a few more cubes in no more than enough water to cover the cubes and ensure I can submerge the stem. Hold until set and then proceed until you reach the bend you want. Each time plunging the stem into the ice bath. You can bend, re-bend, straighten. Just be very careful to not overheat and melt the vulcanite, ebonite or acrylic. If you want to bend a thick bodied stem; start at the thickest part. What you don't want is a crick in the stem you want a nice bend. I've made a lot of cricks that I had to take the crick out of and start over.
Again, heat uniform, (for a thicker, bulkier stem, see comment above) bend, plunge, repeat until you reach the desired bend.
I hope this helped.
Happy shaping!