Awww... glad to hear he loves the harness! Not all cats take to walks, so it's great that Cheddarwurst does! Do you have him on flea, tick, and heartworm preventatives? These are necessary for all cats going outside, even if they're safe on their harness. Also, I've heard that some cats get so excited about going for walks that they might try to dart out the door. One good piece of advice I've heard to prevent this is putting the harness and leash on your cat, and then carrying them out the door, so that they associate the start of a walk with being carried out the door, and will be less likely to run out the door before you are prepared for a walk.