How I bend my downstems.
I use a Bernzomatic fire point Creator tool running on MAP gas. If I plugged one end and put a bowtie on the other I could probably make a curve. As it is now, it does not reduce airflow. Well, technically speaking it cuts down on a percentage of air allowed through but nothing noticeable. I've done 200+ with this method. I've only had about five break at the bend but I'm pretty sure that was just crappy glass. I don't anneal them.