I have a modern Tornado with a carbon mast for a long time. I do not agree that mastrotation has any effect on sail twist. It opens the slot and that is ok in a strong wind. That may be the reason better not to use the traveller as this closes the slot. Twist is not good for pointing because of induced drag. More diamond tension flattens the sail but does not open the top. That might be a good option in a strong wind, but using the cunningham causes twist. Of course this depowers the sail, but the same happens with loosening the main. In the latter case you have the option to power up to the max after the gust. Playing the cunningham does not work properly as the front of the sail will not move up.

I sail a lot of regattas so I know what works. Testing by GPS proofs even more as in a regatta there are too many disturbing elements (different boat types, etc.). To me it looks there is a maximum speed when sailing upwind. The only thing that matters is your course.

The thread applies to sail trim when sailing downwind.