Thats a tough question, because it is completely up to the turkey on when they go to bed. Ive seen one fly up when it was literally to dark to walk without a flashlight, but then again Ive seen them fly up 1 hr before sunset as well. Weather plays alot on this too. They seem to be on roost longer during bad weather, they could fly up earlier due to this as well. As a safe bet, id be there a little after 7, get comfortable and listen since your sunset is around 8 there.