Just chased down snowmobilers

Reminds me of the *** who strung barbed wire across the entrance to a popular public dirt bike riding area when I was a kid. He almost took my friend's head off ... he ended up with almost 300 stitches.

Your situation is a bit different since they're riding on YOUR land, but think of the consequences of your tree placement to somebody hauling azz on a motor vehicle and being surprised at what's in front of them.