Comment 13 for bug 898390

(In reply to comment #6)
> export kcmrandrrc_display_applyonstartup=true
> export kcmrandrrc_screen0_width=1024
> export kcmrandrrc_screen0_height=768
> export kcmrandrrc_screen0_refresh=70

Those can be added to ~/.bash_profile and kdm will use.