[Scribus] HP Color LaserJet 8500 Postscript Driver will not alow me to print custom size media!

[Jelle de Jong]

http://www.linuxprinting.org/show_printer.cgi?recnum=HP-Color_LaserJet_8500

Hello,

I have a HP Color LaserJet 8500DN printer.
And I want to print on a custom size media 21x16cm for example.
But If i want to print from for example OpenOffice 2.0 I have to select
a media type and there is no custom in the list. Zo it takes A5.
If i print the printer gives a error of the incorrect media size he is
detecting trough his guide of the manual input. The windows driver does
have custom size media, but I don't want to use windows.

How do I print on a custom size media.