I just learned about this parameter in a surfacing class, so hopefully my suggestionsare not overly obvious (or wrong for that matter). Is your trajpar parameter in the sketch that you are trying to control, or in the model (needs to be in the sketch)? And I am wondering if you should just use a standard helical sweep? Isn't it the Helical Sweep itself the command that controls the pitch? I thought that trajpar changes the shape of the profile along the trajectory? Goood luck.