Don't top them. They are autos. LST or weight the side branches down then bend the top cola over. Even if you gently bend until you feel it give the bend (it will be sharp) will form a callous and heal within 24 hours. Support if needed but it will not kill it, just deform it. Which is what it is going to do if unchecked.
BTW the top cola will begin growing back upright or attempting to almost immediately. It will just look weird.