Wassname The Bird has just bought a wood burner without consulting me. It is a lovely French art nouveau job from the 1930's. With a 3.5" flu outlet. Modern flu pipe starts at 4". Any idea how to fash a 3.5" pipe into a 4" pipe without poisoning everybody with carbon monoxide or murdering The Bird for buying fFrench antiques? Lead will not work because it will melt and asbestos tends to kill people. Any sensible advice welcome.