In haptic shared control (HSC), an alternative to full automation, a human operator (HO) performs a steering task while being assisted by force feedback on the control device. Human-haptic conflict, caused by misalignment of intentions or different use of reference information, is a source of annoyance and controllers should be designed to eliminate it as much as possible. One way to influence how a haptic shared controller uses reference information is by adjusting the look-ahead time. In this research, a human-in-the-loop experiment was conducted to investigate the effects of varying the haptic look-ahead time in a shared-control preview tracking task. An HSC was designed according to the Four Design Choices philosophy that uses an internal HO model to provide a human-compatible reference. Results reveal a region where conflict is minimal, and no significant in conflict occurs. Subjective ratings by the participants show a similar yet larger region, for which no significant difference in usefulness and satisfaction is perceived. Meanwhile, despite showing a strong `exchange' of authority through human-haptic forces, the error remains low, indicating how the HO adapts to changes in the haptic controller in order to keep the tracking error satisfactory. The results of this research highlight the importance of properly tuning the haptic look-ahead time, while also revealing a `region of acceptance' for which participants are unlikely to notice any change in the haptic shared controller.