I got a copypasta response from them, outlining the steps I already took on their website. Will read it carefully to see if contains any of the info I actually asked for.
One thing is that they expect me to use their web interface to file "prior notice" for every single package I send. I see writing a scraping script in my future..
Is that supposed to be a bad thing? The IRS provides amazing tax advice -- on the phone, for free -- ask any question and they'll give a detailed answer, point you to the exact parts of the tax code that answer your question, and send you a copy of the documentation if you want.
However, if you relay on the IRS' advice and they turn out to be wrong, you still get hit with a tax bill. "Trust us, but don't trust us." Gotta love government.