Thanks for the feedback. I can see the case for matching the shape of the sail's luff - this must be the 'best' position, but that would imply everyone would set their mast up in the same way. I have had advice from the designer / manufacturer to go to the "fat boy" setting, with minimum spreader rake, and maximum mast pre-bend. I am trying to understand the theoretical advantage this offers over the middle setting for each. I gather that with the spreaders raked less (putting them further forward), I will get a stiffer mast, at least in the lower section, and this will generate more power. And if I want even more power, I can ease off the diamond tension and get less mast pre-bend.