That rack will work great with a few modifications. If it were mine I would lose the top rail and vertical braces that attach it to the base. just cut it off with a torch or sawz-all, then clean up the weld areas. After that there seems to be plenty of bars to attach most any RTT,
If you try to put the tent on the rack as is or with bars going across the top rail it will be very high and not that great to wheel/travel with. Or easy to deploy. its already going to be very high up with the extra height of the topper and rack,
You might want to think "as low on the topper as possible".