Wow, that is excellent insulation.
Mine also has 2" of Kaowool, but with the A5 crucible took nearly an hour before the iron melted. I scaled the burner down from 3/4" to 1/2" as I couldn't find 3/4 pipe fittings here. Doesn't really matter with Aluminium as a I can melt an A5 crucible from cold in about 15 minutes, but was probably not ideal for the times I want to melt Iron.