HP OfficeJet Pro 8500 A909a/Duplex FAX Printing?

Is it possible to have my INcoming faxes print on both sides of the paper
(duplex printing)? My duplexer is installed. Duplex printing works when
printing a doc via the computer when I set it up to do so, but, when I get
multiple page faxes (they print automatically when received) I'd like for
them to print on front and back. They don't and I don't know how to set it
up to do so. Surely it's possible. This machine brags about being "green"
so it seems like a two page incoming fax could print front and back on one
piece of paper. Again, the duplexing works, but just not in fax mode.
Thanks,
Monica