JBoss Messaging Slow Consumer Messages Clustering

I have JBoss EAP 5.1.2 (incl. JBoss Messaging 1.4.8) with JMS clustering.

The consumers are slow (several minutes) with various execution time (1-30 minutes) so I enabled the message redistribution (ClusterPullConnectionFactoryName).

My ConnectionFactory attributes are:

true
      true  
      true
      1
      true
      true
      true  
      1
      true

Of course, the corresponding post office is clustered as well.

However, messages are not distributed equally in the cluster, some nodes are fully loaded, some of them are almost idle.

Please, do you have any hint how to (re)ditribute messages equally in the cluster?

Thanks