hey folks, I've built a 4' x 8' coop and have it well insulated for winter. I want to put wheels on it so I can move it around easily, but I'm not sure what kind of wheels to get and how to attach them securely. The coop probably weighs about 300 pounds. Canadian Tire has wheels for wheelbarrows that are 8" in diameter and it says they take a 3/8' axle. Any ideas?