Can you not find a place closer to their entry to the field? Maybe there's a point the deer seem to frequent as they enter the field? Mature bucks will have a tendency to show up into the fields closer to evening. The thing is, there's a good chance these bucks were already up and on the move the same time the other deer were. Sometimes they have feeding/holding areas they hang around inside the woods, before finally entering the field closer to dark.

So maybe try hunting some trails or other food source just inside the woods...get between their bedding area and main food source....the holding food source can be just as good if you find it.