So try setting the graduated visibility scale not from 6,000 feet, but from 1,000 feet. This gives 9,000 feet for the graduated visibility to `phase in` rather than just 4,000 feet.

Also set the ground level visibility to 5 miles (500) for cloudy and maybe 6 miles (600) for clear (you can obviously set this to your liking, but keep it less than 10. I forget the exact real world figures but the horizon at ground level is about 6 miles away, 12 if you're 18 feet above, or something like that) - remember, all you're doing is creating a ground `haze` effect, not actually setting visibility.

Finally, adapt that top of the visibility level to integrate it with cloud layers - setting the top to 500-750 feet above the lowest cloud layer gives you the feeling of popping out of the clouds when ascending.