Meg, unfortunately I can't help with the aggression problem, but wanted to address the winter problem. As you may or may not remember, my mom has an "outside" kitty. They live near Green Bay WI, so it gets pretty cold outside in the winter. So what they did was build him a little house in a protected corner of their house, and put lots of nice warm blankets in it. He not only survived the winter, but thrived! He actually used the house, and the protection from the weather plus the heat loss from their house was enough to make a nice comfy spot for him. My mom takes walks in the woods behind the house and whenever she would go, there would be Goofy, bounding along in front of her, making tiny little kitty prints in the fresh fallen snow.

So I guess what I'm saying is that if you can't get him more tame by winter, build him a little house to use to protect him from the weather. Put his food nearby so he knows there's food and shelter, and he will come. Goofy has "progressed" and now hangs out in their garage.

The only other thing I can think of is to trap him and keep him in a confined area. As others have mentioned, and as Magoo has shown, sometimes being in a cage for a few days makes them realize their ship has come in and allows them to accept the good life that we want to give them.

Good luck with him!