A wise old hunter, maybe the smartest guy I know, maybe... taught me this. Make your pen big enough to be a bit larger than your corn throw circle and tie the panels on to your T-posts to be about 2 feet off the ground. Pigs can come and go, but not the cows. A tip if you hunt from a blind is to put the panels on the far back of your pen on the ground, so when the corn starts exploding, they have to run toward you somewhat to get out. T-post on each end and one in the middle or the panel gets kind of floppy, but still works. Two seasons for me with no cow entrants. Just mount your camera on one of the t-posts or move it inside some on another.

Here's a thermal view, you can see the panels still.

Charlie