Non Standard Sized Printing on 9500DN

I have a client with 2 x 9500DN Kyocera printers. He wants to print large jobs (so manual feed is a no go) of 320 x 160 sized or other weird paper sizes. How can we set up his printer to do this without jamming? I have tried A3 but that doesnt work either. Is there software that over rides the printers sensors?