The IETF is currently standardizing a light-weight protocol framework for server redundancy and session failover: reliable server pooling (RSerPool). It is the novel combination of ideas from different research areas into a single, resource-efficient and unified architecture. Server redundancy directly leads to the issues of load distribution and load balancing. Both are important and have to be considered for the performance of RSerPool systems. While there has already been some research on the server selection policies of RSerPool, an interesting question is still open: Is it possible to further improve the load balancing performance of the standard policies without modifying the policies - which are well-known and widely supported - themselves? Our approach places its focus on the session layer rather than the policies and simply lets servers reject inappropriately scheduled requests. Applying failover handling mechanisms of RSerPool, in this case, could choose a more appropriate server instead. We have already shown that our approach is useful for homogeneous server pools. But is it also useful for heterogeneous pools? In this paper, we first present a short outline of the RSerPool framework. Afterwards, we analyse and evaluate the performance of our new approach for different server capacity distributions. Especially, we are also going to analyse the impact of RSerPool protocol and system parameters on the performance of the server selection functionalities as well as on the overhead.