Put it on the front of the mast, down about 3 or 4 inches, with the halyard through the strap. This will keep the halyard and the knot away from the foil.
Furler hangups are no fun. My last one was due the my spinnaker halyard - I'd led it to a ring on the pulpit rather than the mast. It got a bit of slack and snagged the upper swivel during a furl. An exciting few minutes on the foredeck until I figured out the issue.