Designating a key column on a metric extension that is already deployed to a Host Target

I have created a multi-column, multi-row metric extension and have successfully applied it to a host target.  Upon triggering it, I receive an error that the metric does not have a key column designated for it. So, I go to modify one of the metric extension's column to be a key and it does not allow me to do so even if I tell EM to create a new version of the metric. Is the only way to achieve this is to delete the metric extension, re-create it and re-deploy it to the host target?