[Therion] User-defined symbol with orientation, l-size and r-size options

Hi all, I would like to draw a large water-flow,not as a simple line, and show its direction. I try to define a user-defined symbol with orientation, l-size and r-size options. But Therion (v 5.4.1) answers that theses options are not valid with type u. Is there an options or a way to enable theses options? Thank's Emmanuel