We do the exact same thing, and here's our template for adding a single model to a static global collection.
<?xml version="1.0" standalone="no"?>
<!DOCTYPE Import SYSTEM ".modelinggateway.dtd">
<Import>
<!-- **************************** -->
<!-- Template for adding a device to a global collection -->
<!-- %(batch_id)s for locking/unlocking purposes -->
<!-- **************************** -->
<Global_Collection>
<GlobalCollection name="%(GlobalCollection)s" Security_String="ADMIN" >
<Device ip_dnsname="%(IP)s"
model_name="%(DomainName)s"
%(Credentials)s />
</GlobalCollection>
</Global_Collection>
</Import>