How can I set the output tray on a WC7970 for envelopes? Settings allow for selecting output for fax, copy and print, but not envelopes. I would like envelopes to output to center tray vs left side tray. Both tray 5 9x12 envelopes and tray 1 #10 envelopes default to side tray. This is a replacement WC7970 and our original system outputed envelopes to the center tray.