Floating line is good for A-Sails because they are less likely to go under the boat when you screw up a gybe. They don't make any difference if you use a symmetrical spin or if you gybe it through the forward triangle.
There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
Shakespeare, Julius Caesar IV, iii, 217