I would get in really early, I mean really early, hour before shooting light and set the decoy at the edge of the green field. I would then sit beween the decoy and the roost, with the decoy in range. Do a fly down call and wing flap when it is still half light (before shooting light). Then wait for the tom to pitch off the roost. I don' t think turkeys can see any better than us during low light. He will rely on the sounds you make to tell him a hen is down. This type of set up has worked for me several times. Have even hhad to hold the gunner off from shooting until it was legal shooting light once.