That should work...how are you interfacing to said printer, I didn't think the GPL builds of Virtualbox had USB passthrough support or are you using the PUEL builds ?
That said I have found the Postscript emulation on some low end printers to be somewhat incomplete. Why not use the recommended hpijs driver to talk to it in it's native PCL..you will probably find it will be faster like that and you may get more features from the driver.
http://www.linuxprinting.org/show_driver.cgi?driver=hpijs&fromprinter=HP...