As they are still too young for a full harvest, and it is past harvesting stage (when spears are about 8 inches tall, and not branching), then you should, as you have suggested, just leave them to grow. Eventually they will grow tall with ferny leaf growth—too tall for the hoop frame, but at that point, perhaps the rabbits won’t be as interested in the plants. Wait until fall, after the foliage has died and browned, before cutting the ferns down to about 2 inches above the ground before winter. The leaves will help the plant make food for itself to survive over winter and grow healthy spears next year.
As they are still too young for a full harvest, and it is past harvesting stage (when spears are about 8 inches tall, and not branching), then you should, as you have suggested, just leave them to grow. Eventually they will grow tall with ferny leaf growth—too tall for the hoop frame, but at that point, perhaps the rabbits won’t be as interested in the plants. Wait until fall, after the foliage has died and browned, before cutting the ferns down to about 2 inches above the ground before winter. The leaves will help the plant make food for itself to survive over winter and grow healthy spears next year.