How to configure screen modes without EDID

When EDID info is not available AmigaOS 4.1FE seems to default to 640x480x8 and no other screen modes are available. I've tried to add a monitor file with tool types with DDC disabled and frequency limits and some modes defined which then show up on the monitor tab of ScreenMode prefs but not on the main tab so they can't be selected. I've also tried defining modes with Picasso96Mode but it defaults to something like 72Hz and I cannot edit it without attching to a card and when attached to the card it says for even the 640x480x8 mode that size is too big for the card for any action. What is the correct way to define screen modes when the monitor does not send and EDID and so no modes can be selected? I never used RTG or AGA so this screen mode stuff is completely new to me.