I have a ram in my tank which doesn't have a top. It's rare to see him anywhere near the top of the tank. He sticks mainly to the bottom. I've never had a fish try to jump, but I also have a lot of floating plants.
I had a ram jump on me once. It was because I got home in the middle of the night and flipped on all the lights at once. Fortunately I saw him flopping on the floor and got him back in the tank safely. That was on a rimless tank with the water at the very lip too.
With that being the only occurrence; I wouldn't worry much.