The pattern made from some factory vest.
6 meters of carbon heating flex tape (www.carbonheater.us) placed on back and both sides. By touch carbon is a little bit like a loose weave silk. It's very soft but strong enough.
Because of big length it provides uniform heating of body.
But as you can see sewed contact is colder than the tape itself (left contact).
Wraped contact (on the right) is more hotter than tape.
Place two pieces of carbon tape together on each other with little overlap and sew it on.
As you can see the connection place is not hotter than the tape itself.
I use it with an adjustable controller.