Your camera metering would still be inaccurate even you mount on your flash. A lot of times would depend on your experience. Depend your location, is it open area or indoor. If it is indoor, is the ceiling high or low.
Thanks Reno. I can't find anyone who share their experience if we need to check built in light meter or not during flash shooting. Most of them only share shutter speed control ambient light and aperture control flash power only.