Do I have a MC on my hands?

I've got a big, beautiful cat named Fuzz. He was (as far as I could tell) feral when I first spotted him in my backyard about 18 months ago. I live in a pretty rural area near the base of the Appalachians in north Georgia and I've met several cats that seem to wonder out of nowhere and act as if they've never be domesticated. Anyways, it took me about two months to be able to get close enough to touch him; we would play the "how close can I get before you run away" game and I continued to be able to get closer and closer. At the time, he appeared to be no more than 6-9 months old. I was intrigued because he had a wild look to him.

Over the past year and a half, Fuzz has grown substantially. He got rather large last winter but now he seems to be substantially bigger. When he's stretched out, he's right at 3 feet long from front paws to base of the tail and is currently weighing somewhere between 15-18 pounds. He has a lot of the characteristics that I've heard associated with Maine Coons (big paws, tufts of hair between paws, "wild face", multi-layer coat, tufts of fur curling out of ears, very affectionate) but he also lacks some (tips on the ears; he has small ones but they're not really noticeable). He's the only cat I've encountered in my life that seems to fluctuate dramatically between seasons; he becomes really scraggy looking and thin in the summer with a strip of long black fair down his back but becomes a big, beautiful fluffball that weighs at least double in the winter. He's been an outdoor cat exclusively as I already have three indoors and the other older cats do not appreciate his playfulness; I've also let him keep his jewels just in case I ever decide to try to get some Fuzzie kitties. I've also heard that MCs continue to grow until they are about 4 years old? I can't imagine him getting too much bigger!

I know he can't be full Maine Coon but I'd like to see what the community thinks about him being at least part MC. Maybe he's just a big docile wild cat, who knows? Here are some photos. His size/length isn't as evident because he's gotten so darn round in the past couple of months putting on some winter fat.

http://www.gryphonics.com/fuzz.JPG
http://www.gryphonics.com/fuzz2.JPG
http://www.gryphonics.com/fuzz3.JPG
http://www.gryphonics.com/fuzz4.JPG