OK so I loaded my safe onto the ST this morning using a strap, a floor jack & my Motorcycle jack. I tipped the safe against the tailgate, put a strap (for safety) around the door opening wheel. Hooked it to the bed eyes, put the Motorcycle jack under it & raised the safe off the floor. Once it got to a certain height, my son putt the floor jack under it. We raised it until it started to tip in the gently let it rest ON THE TAILGATE! We had a cardboard box in the bed so we could easily push the safe all the way to the front of the bed. NO DAMAGE, NO ISSUES, & NO PROBLEMS.
SO...The final answer is YES the ST tailgate CAN support a Winchester 26 gun safe ON THE TAILGATE without any damage!