Lurch wrote
Is Lead a good or poor conductor of heat in comparison to the steel
clips ?

I think you'll find something non-conductive better. You seem to be
struggling with this heat\melt\conduct equation. Wood or plasterboard
would be the better material to use.

Totally agree about non-conductive, but I'm not sure about wood. I would be
worrying about it burning. And plasterboard + PVC would be too thick wouldn't
it? As a suggestion, how about cutting doughnuts out of those fibreglass mats
used by plumbers for shielding a blowtorch?

Peter