That stayed outside almost always. But when her situation turned bad *too many loose dogs roaming around* she had to keep her cat indoors, with no more outside privledges. It was tough for the first week or so, but she grew accustom to being indoor only. And never tried to get outside again.
I am sure with it becoming colder outside, it is the very best time to try to keep him dwelling indoors. Because cats dont seem to like the colder weather, and will be inside more anyways. I would just not let back outside, no matter how many whimpers he tries to make
PS> my mom bought a rabbit harness from petsmart, and she uses it for her "fluffy" cat, because it fits better than the kitty ones. Maybe you could try to get one of those, instead of a kitty harness. *I also think they are cheaper for the rabbit ones* Hope this helps