In hierarchical reliable multicast schemes, the number of repair proxies and their locations influence inter-receiver delivery delay fairness. Improving inter-receiver delivery fairness is beneficial to synchronized communication in multi-conference or interactive system. In this paper, we propose a scheme to find the optimal locations of repair proxies that can improve inter-receiver delivery delay fairness maximally in heterogeneous network environments when the number of available proxy is limited. Our evaluation results show that if repair proxies are placed by the proposed scheme, delivery delay fairness can be improved by 0.05 maximally.