Hi Wayne,

Here is an article which says that it's not recommended to have more than one instance installed on a single cluster node.

http://www.sql-server-performance.com/articles/clustering/clustering_best_practices_p1.aspx

Since you are saying that you have just 2 instances and that too being pre-prod databases, I stongly believe that you should not have any problems or issues with that implementation. To let you know, we have both Development and Production clusters with multiple instances sitting on each cluster node.

Thank You,

Best Regards,

SQLBuddy.