beginner's how heavy the crankbait question

I'm a fly tier and fly fisherman. I don't know much about
casting rods or bass lures. But I have figured out how to make
crankbait lures with a relatively fast easy and cheap
method (no carving balsa wood or injection molding a no kind).
You can make these wigglers as large or as small as you want,
and as heavy or as light as you want....with a wide, slow
shallow diving wobble, or with a tight, faster deep diving
vibration. Better yet, they're (mostly) soft bodied, so
fish bite and hang on, rather than spitting right away.

But how heavy is right? 1/4oz?
3/8oz? 1/2oz?

What is the most useful weight to make a 3 or 4" long
crankbait?