Indeed. Maybe that function does not fit for that purpose.

Curve.getParmeterWithLength() brings a better result.
Though it requires a bit complicated process.

Here's a sample code as attachment.
(I think there must be cleaner codes)

Hiroyuki,
thank you so much! your script works exactly the way i was looking for.
i also checked your website -- awesome stuff.
how did you learn it? i can program, but till now i didn't find the functions of SG and illustrator so well documented. is there any good reference that i maybe have overlooked?

thanks again & a nice day
andre

We'll be working on the improving the documentation and creating tutorials during the coming year, please stay tuned!

Andre,
AI SDK's document can be a good reference of Sg's functions.
However, to understand some of functions for bezier curve
that Sg (AI SDK) has, it's unavoidable to face
the math definition of the bezier curve.
I learned about it by reading various websites of math.
It was a process with confusion and annoyance,
and it'll be same for most of Sg users -- who intend to
design, not to study math.

I think there should be an intuitive tutorial for
scripting bezier curve.
I'm considering to write it.

Hiroyuki & Jonathan,

thanks for the replys, i'll also try that i get better with it so i can contribute as soon as i can something. cheers guys!
andre