Ok, it looks like the failure is peculiar to our test b/c the len(db + collection + index) > 128 chars (the test appends a guid to the collection name which adds 32 chars). Shortening the index name will definitely fix it, but, as you said, may be costly one-time deploy.  Another approach would be to just grab the first 4 or so chars from the guid to make the collection name unique? Hmmm.