As of jPOS 1.6.5 r2845, we added a new input-space property to the TransactionManager. With this minor addition, you can easily distribute the load among multiple Q2 instances running in the same or different machines. 
I'm a true believer in long-lived lightweight Q2 based components. Now thanks to our very simple Space interface and Bela Ban's awesome JGroups that allowed us to implement the ReplicatedSpace, creating this kind of jPOS clustered setup is now feasible.
TransactionManager input-space
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jPOS project founder