Have you tried hunting the field edge in hopes of catching a cruising buck?
In open country, that is pretty much all we have to hunt BigSlam. Most "woods" are 5-10acres around here. 20acres of woods is huge to us. Been hitting mainly pinch points, funnels, fence rows and travel routes. Yesterday I hit some fence rows where they connect with CRP fields on either side of the fence rows. Not a buck to be seen yesterday.