Removing RPA from cluster

I have an older Gen RecoverPoint appliance that I want to remove from my cluster.  I just replaced an older Gen appliance with a Gen5.  Now I have 3 Gen5 and 1 Gen3 appliances.  I want to remove the last Gen3 and operate with just 3 Gen5 appliances as they are fast enough to keep up.  Is there a documented procedure on how to remove an RPA from my cluster?  If so I have not been able to find it.  Thanks!