Thanks for the pics and information. I had thought about going with an octagon or even 16 sides to the cupola so it would have some flat surfaces to make building and covering it easier. Unfortunately for me, I really want it to look round. What I'm seeing in my brain is something that looks like a bull thistle without the spikes to it, if that makes sense.
Eddie
Could you steam the cedar shingle and then bind them around a piece of PVC to give them some curve? That way you could use bigger shingles?