how to get custom rendering settings, dpi, angles, etc to print?

[gregnh]

i have noticed in scribus 1.5(linux) that there is an option in the export to pdf for custom halftones, dpi, line angles, even dot shapes. as a printer that needs screens of 45 & 55 lpi this is huge. however, when i export these pdfs & print them i get the usual default screening, too fine to capture on silk screens. i also notice they are available for cmyk only? has anyone gotten this to work and can they point me in the right direction to make this happen. thanks.