In article . com,
"Phil" says...
4" wide lead flashing (not the sticky kind) wrapped once around forming
a capillary joint with plumber's solder and a BIG blowtorch applied.


I'd have thought a strip of copper sheet would be a better idea.
You're unlikely to be able to form an effective capillary joint, but
you could run enough solder down from the top to create a good
seal/mechanical joint. As you say, lots of heat required.