Per,
Since your front floor is still not installed, Weld some angled steel inside the rear of the front frame rails. This is the lowest point that gets the load from the lifts and floor jacks. This area usually deforms and collapses from all of the lifting force. You can grind the areas where the holes are so that the metal is not visible from the underside. I did this with my convertible when I replaced one of my bent rails, after seeing done on another website.