Postscript through 400 ignoring tray specification

We are using FTP "get" to retrieve  Postscript data from a customer to
print at our facility.  The customer is also requiring that we print on
their custom media, so it would be handy to specify what tray, or source
drawer, the media is fed from when printing these labels.  The spool file
type is *USERASCII.  No matter which tray is specified on the spool it
seems to feed from the default tray as defined by the printer.  The
printers are various models of Lexmark and all seem to perform in the same
way.  My work-around for now is inserting a section of postscript code as
output from a print-to-file from a windows print driver specifying tray 2.
Has anyone had experience with this loss of control and if so did you ever
find a solution?

Thanks,
Darren Strong