@Northsea

Mast rotating was indeed as tight as possible. And what you describe here is a little bit where I'm afraid of. But reading your input, we might be able to fix it a little.

Just to be sure: After measuring the sail in this way: I suppose we measure the mast in the same way? (with the rope?)And the aim of the whole exercise would be to get it as close as possible?

@ Sam

Yes I'm starting to realize the subject of that topic is rather the same, but didn't understood that before because of the terms used (e.g. jib reaching) I will read it!