How to prune overlapping groups

Here is the process I am using when I see groups whose missions overlap too much:

• send an email to all group members using the Email tab. some example text:

As part of standard pruning, this group is closing. Please continue the conversation in the more active High Performance group - http://groups.drupal.org/high-performance. All posts will be moved there. Please adjust your notifications/feed subscriptions accordingly.

• delete the less active group, and choose the option to move content to the target group. Go slowly here, and get it right.

I could add a feature which moves email subscriptions and even rss feeds to the new group but thats not in place yet. Comments on the value of that are welcome. I rather like it.