Just a couple quick question- is there a reason the cannon is raised on that single stud round plate? In addition, can the rear-mounted gun hit infantry? It seems to be a bit too elevated. Anti-helicopter attacks would be fine, as would attacking largish lumbering behemoths, but not being able to shoot troops may be an issue. *tries to think if there are any hinges that small that rotate both 180 degrees...*
Other than that, it seems a bit large for what I usually consider an ATV. On the other hand, ATV simply stand for "All Terrain Vehicle," so I'm probably making a bigger deal out of it than I should.