Yeah bunny fur is a great insulator. Make sure when testing for "doneness" that you take your thumb and put it up under the rabbit's breastbone so you're checking the thickest part of the chest. I've had some 8-10 lb rabbits take hours to warm all the way through even after being thawed in the refrigerator for a week. Dealing with multiple smaller rabbits or even guinea pigs is a lot easier.