[Fitz]

Heat? Are you crazy?
That is what sweat shirts with hoods are for.
In the summer in Phoenix you are dying for cool air. I have a top like Mul suggests to keep that bloody sun off my head. It is the only way to go in the summer. A open roadster in the winter with heat makes no sense as the air just penitrates your neck. There is enough heat coming form your firewall to keep you comfy with a jacket. Put a ski jacket on and forget it.