I shall watch the results of your first firing with keen interest, Curl.

That stuff certainly looks the part, lets hope it performs well without reservation.

I have always been mindful of the wide variation in materials used to make 'foam', from rubber through polyurethane to polypropylene etc, and even the brittle 'florist foam', whatever that is, and was never game to experiment myself.

Polyurethane foam seems to be the preferred stuff according to Graeme Wright, it is blasted to granular powder apparently and doesn't burn or melt in the bore. Do you know what that backer-rod is actually made of?

Good luck, mate!