I built a raised bed, with three bands of barriers, to keep out birds and squirrels. The hardware cloth, with 1/2" grid, has been effective. But the other two barriers have failed to keep out our very industrious squirrels. They can actually eat through chicken wire, and of course the plastic bird netting is no obstacle at all. I would appreciate your guidance for what kind of barriers to use. I am assuming that I will need to replace the plastic barriers with metal. But what GAUGE of metal, and what size OPENING do I need to keep squirrels from either biting or squeezing through? Thank you!