Great chart but I'd be nervous putting my snowmobiles on 6" of ice!! There are lots of spring holes up here where 2 feet of ice can turn into 2 inches in a hurry. I was cooking along on real good ice a couple years ago and found myself going across a hole about 6 feet across that gave way as I went over!! Luckily I was going fast enough that all I felt was the rear end drop. Talk about stop your heart for a second. I was alone and about 2 miles back on a lake with no one else around. They might have found me in the Spring if I'd bothered to tell the wife where I was going.. Dumb!!