[Sunhelp] selecting input tray when printing

[nathan]

i'm tryin to setup so users can print to our HP 5si and select a
particular input tray

we're using LPRng, and its docs say to use the -Z option
eg:
    -Zlandscape -Zportrait - select landscape or portrait orientation.
    -Zduplex -Zsimplex - select duplex (both sides of a page) or simplex
(single side of a page) printing.
    -Zletter -Zlegal -Zledger -Za4 -Za5 -Zenvelope -Ztransparency -
select a paper size
    -Zinupper -Zinmiddle -Zinlower - select input media from the
appropriate input tray
    -Zmanual - select input from the manual feed

some of them work (like -Zlandscape) but the ones for selecting input
tray don't
anyone have any ideas on this?
thanks!
nathan