[david s]

cvdukes,
I don't think coathanger wire is a good idea, its too thick and provides a path for heat to escape to the outside. I use thin wire about 0.5 mm twisted together with aloop at one end and some legs to sit flat against your dome. This is held in place by a layer of concrete and these wire ties act as depth guages for your vermiculite layer and as anchors for your mesh for your ferro cement outer shell. Works a treat.