The rear slider will be welded last. At rest with the full weight of the vehicle resting on it the eye bushing bolt should be about 70% toward the rear. I sat my 250lb butt right on the center of the rear frame to simulate the box being bolted back on and get a start position. But I will slot the mount holes to get it ideal with the correct weight on the frame (The box) then final weld it. This pic shows the position with no box and no substitute weight on the frame. It moves a little bit when I sit on the rear.