As a hobbyist weldor, I strongly recommend bolting
an auxiliary receiver to the frame.
Bolts fail in stages with plenty of warning. Cracks in the frame, the receiver assembly or the welds will go unnoticed until something breaks.
After that, be careful on how much mass you put back there. A whole lot of bouncing goes on. So your hitch, bike rack or other storage tray will be dealing with lots of live load.
Also check this recent thread: