Ok, I made some sketches:
Frontview:
We like to show version
A
But because we take the side of the boat we choose for
B
(turning the sail 90 degrees)
We really don't want
C
Right?
Topview:
We like to show version
A
But because we take the side of the boat we choose for
B
(turning the sail 90 degrees)
If choosing between
C and
D, we rather have
C instead of
D.
Right?
so I made a preview of my suggestion and Craig's suggestion

It's still optical illusion.
To me:
The right one is topview C and frontview B
The left one is topview D and frontview B
But I guess for another person it might be:
The right one is topview C and frontview C
The left one is topview D and frontview C
To me a sail is always bulging and not concaving on an image.
Keep in mind that you can see both images different ways
If you see - on the left image - a bulging sail, than the sail is turned backwards. (like topview D)
If you see - on the right image - a bulging sail, than the sail is turned the right way. (like topview C)
If you see - on both images - a concaving sail, than both options are wrong. (casue it's concaving)
And this way the right one the sail is also turned backwards.
So my first option is still the best to me, for I don't like a straight (sqaure) sail.