Lets see, since this vector tube script only works on vector paths. Since you are making you TEXT "A" in the vector text format. vectors have two sides to every vertical and horizontal line.
Even if I turn off the fill properties and set the stroke to 1 it stills creates two lines around the whole "A". So that means the script will follow both lines up, down and left to right.
But if you use the pen tool and draw a vector line and then run the script it only applies the tube one time to that line. Which is what you want to achieve with your A. There might be some fonts out there where the stroke is a line line with no width to them except for the single stroke, but I don't know which one and I played with a few of them. I also played with Objects>Convert Text to Curves and convert to path.
The only way I know of to acheive what you want to do is to use your pen tool and draw a single line around the inside of your text shapes and apply the tube script to those vector lines.... hth's
Here's a quick example of what I mean
http://www.paulbunyan.net/users/hale...ube_script.jpg