Increasing mainsheet tension decreases rotation and twist, but not much
Not true.
1, Mainsheet tension will decrease twist.
2, Mainsheet tension will effect mast rotation.
but this depends on the sheeting position relative to the boom (if present).
If when sheeting in, the sheeting point is aft of vertical(behind the back beam), the boom
will be pushed forward, now assuming the boom is attached to the trailing edge of the mast (most are) then the mast will be pushed forward and so rotated more (in the absence of a limiter). Reverse is true if the sheeting point is forward of vertical.
If there is no boom, then it's the position of the sheet mount on the sail; Generally I would think that the sheeting point would be forward of vertical so get control of the sail with no boom present.
