Moin Uli,

the knots are the result of trial and error. Hopefully they don't slip through the cleat. I can lower the gennaker just that the boom doesn't slip from the pintle. When single handed I have to drop the gennaker before I can right the boat. Wouldn't be nice to drop it and the pole slips from the pintle on the water.
Usually I adjust the halyard tension once on land not on the water unless it is totally wrong.

Cheers,

Klaus