No, currently there is not a "X Offset" parameter, to shift the object along the spline.
Although its implementation seems simple, there are some problems to solve, as how to extend the object beyond the spline (use the direction of the last vertex ? ).
The best option for this case may be:
1) Modify the spline manually, extending it along the desired direction.
2) Use Generator->Limits->Padding Start, to shift the start point of the RC object.