Step 8: Cut and Sew chest strap and attach the stretch sensor.
You'll have to measure the length of strap to your individual body type. I sewed an extra strip of fabric around the strap, so the wires can safely sit inside. In the front, where the stretch sensor connection is, I sewed a 'sleeve' of fabric that would loosely cover the sensor so it wouldn't get rubbed or damaged.
In the back of the chest strap, I made a simple shape (like on a backpack) for tightening and loosening the strap. I had the shape laser-cut out of clear acrylic (see image), but you can make it any way you are able to.