I would add to use enough of the angle iron runners or square channel iron runners. So that all of the plywood lays on enough flat angle or square channel iron, to be properly bolted down. This helps remove any excessive vibration that could cause a excessive up and down bounce.

At the end of the angle iron when you square and weld them. You end up with a many sided type metal circle at the end. Could be a 12 to more little angles around the outer circle. Remember to allow the plywood to over lap the metal frame by at least 4 inches to six inches. So you can staple the Padding and Carpet underneath. Makes a soft safe edge if it strikes you while turning. Dog does not run there, but your knees or body will be close to it while it spins.

When a dog is running one of these tables. A lot of kinetic energy and movement of mass is taking place. Be careful and be safe, keep children and strangers away from it. Cheers