I have a TT and have backed it up with sway bars, but it's a calculated risk. Everything depends on how tightly you make the trailer turn. If it jacknifes (jacknives?) it could actually bend the sway bar, or even pull it off of the tongue of your trailer. When I have to back mine into the space where I store it I take it off -- it's just too tight. Sometimes when I know that there's virtually no turn in order to back in to a spot I leave it on. When I'm not sure I take it off just to be safe.
So ... size up the situation and decide what's safest for the trailer. You'll get a feel for what's comfortable, or break something in the process.
Laura