Does anyone have a working example of getting jsonp from the HathiTrust bib API?

I can get straight json (it seems to ignore the callback parameter)
http://catalog.hathitrust.org/api/volumes/brief/oclc/3967141.json&callback=mycallbackfunction

or jsonp with some unfortunate notices at the top (and yes, I just emailed their 'feedback' address and asked about this.)
http://catalog.hathitrust.org/api/volumes/json/oclc:3967141&callback=mycallbackfunction


I'm wondering if I'm just missing the correct url/syntax.