ctxadmin,
Yes, it is possible to default a different tray for the Xerox 5335. If you download the Xerox 5335 Administrator Guide clicking here you will also be able to find the steps needed on page 115.
Basic Instructions:
When printing received faxes, our Xerox 5335 defaults to tray 1 as the paper source. Is there a way to designate a different paper tray for this function?