I calculated that four foot diameter would be enough and the cages looked huge around the babies. The deer have been able to snag a few buds within six inches of the cage.
When I have some time, I'll take them apart and add another 6 feet of fencing to increase the diameter to six feet and increase the protected area another foot from the bush. The bushes will be bigger next year.
I knew they couldn't get anything from the top but never expected getting to the bushes through the fencing.