Please do not use a flame to weld polycord, the fumes are
toxic!
Besides, using a hot air gun works better. Put the cord behind a hole in a piece of aluminum to shield it so only the ends are exposed. When it gets good and soft push it together making a round ball at the joint. Hold it in the 'L' of a piece of aluminum angle to keep it straight as it cools, then cut and sand the excess off. Never had a failure.
Good luck, and say hi to Joe and Tom for me!