We have an HP 455ca.. and use osX with the rip software running on classic. it works fine
either use the 455ca printer description from os9 in the osx printer description folder (it works fine) or use the hp 800 ps description (you'll have to create new page sizes based on the old 455 settings)
-make sure the hp rip software is running when you build the printer.
-you will use the settings in the print menu to plot to file under output options.. save file as a post script file (not pdf) and then drop onto your rip software icon running under classic and it should print just fine...
note: if you use the 455 description all of the usual print settings will be under the print dialogue, and if you use the 800ps then the settings can be adjusted upon loading the file into the rip software provided by hp.
works great just don't use any patterns below the first row or you will receive a 'free bad address' (we stopped using patterns all together)