Adding a node to APM/SAM using powershell with WMI credentials

I have figured out how to add a node to APM/SAM using powershell, but it only works with ICMP (or snmp) as the ObjectSubType, not with WMI (well, it adds it, but web interface errors after doing so and I can't even go back and update the credentials)

I can add it as ICMP, and then change to WMI, but I would prefer to do this programmatically.

I assume I subsequently have to add a set of WMI credentials (in my example, I need to correlate credential '6' to that node) after the initial node creation, but can't figure out how.

Can anyone shed some light on what else I need to do to automatically provision a node using WMI and a set of credentials (which might already exist at which point I can search the credential ID, or might not, and have to add them as well)?

(v5.5)

Thanks!