Cool subject. I ran into this thought about 6 months ago in my town when I found a small area near a state road that once had two colonial homes on a long gone side road to them.
I found 3 of the biggest trees around. One is about like yours, 5 feet wide?. The other two are close. I also found one big monster near my home, near a river, and the beavers tried to kill it by chewing all the way around. But the tree has deep wrinkles? if you can picture it, and they can't get the outer bark in there, so somehow the tree still lives.
PS I have a 4+ foot wide oak in my yard