Thanks guys.
The trailer is a Dinot which has fiberglass sides. Internally there are some channel steel and that is what the rail brackets are mounted to. I'll look into either adding a third rail or running a pair perpendicularto the ones on there.
I built the small Dinoot, worked closely with Scott to assure the fiberglass didn't crack under weight of RTT offroad. Ended up fabricating steel brackets to transfer load from fiberglass sidewalls to trailer frame.
As Frenchie wrote, third crossbar makes all the difference.
Eddie, Sorry did notice your post before. For a 56" wide RTTs we set crossbars 36-42" apart. For 72" wide RTTs we go with 3 cross bars. On your Dinoot, I believe the original owner added some steel framework on the sides. If so, that could be used for repositioning the crossbars