Exactly. I would set the meter at double the box speed, in this case 800, take an incident reading with the flash meter, and open the aperture 1/2 stop more than what the meter says for the shutter speed you've selected. This should give you nice even lighting without overexposing.
Interesting that in flash mode the meter offers 90, 100, 200 and 400 as shutter speeds. My lenses are 125, 250 and 500.