Its hard to lure a mature Tom across a field.
100% right!! If I have that as an option, unless the tom is hot, I try to relocate to the edge of the woods/field on the same side of the field as the tom.
I've heard it said a tom usually won't fly down until you can see colors.
Maybe you should try to roost a gobbler at night and set up on him before he starts his morning gobbling.