Modular robots are mechatronic systems that can rearrange their connectivity to create new topologies to accomplish diverse tasks. In previous work, we have studied a modular reconfigurable robot (Slimebot) characterized by a spontaneous inter-module connection control mechanism. The modules of Slimebot connect to each other via a functional material which guarantees physical coupling between the modules. Here, we investigate the effect of heterogeneous inter-module coupling strengths on the adaptivity of Slimebot (here measured in terms of structural stability and locomotive speed). Simulation results show that a certain amount of heterogeneity improves the adaptivity of the system compared to the case of homogeneous modules. The only assumption that needs to be satisfied by the system with heterogeneous couplings is compliance to Steinberg's energy minimization theory.