Human-human physical interaction has proven to be advantageous especially in contexts with high coordination requirements. But under which conditions can haptic communication bring to performance benefits in a challenging cooperative environment? In this work we investigate which are the dynamics that intervene when two subjects are required to switch from a bimanual to a dyadic configuration in order to solve a complex reaching and stabilization task of a virtual tool in the presence of an unstable dynamics. Results show that dyadic cooperation can improve the performance respect to the individual condition, while minimizing the effort. However, in the joint task, when the stiffness of the system becomes harder to manipulate the feedback delays appear to be critical in determining the maximum achievable level of performance.