Jacking points are put in very specific places and to be used under specific loading conditons, for a reason.
Do you want to know about a DC-8, or a light general aviation airpalne?
As has been discussed over and over now, every airplane is different. What applies to one airplane does not apply to another.
You seem to believe that you've learned all you need to learn about the wing by lifting up on it. You've created some degree of upward bending moment...perhpas not bent the wing, but you've applied the moment. What if that's not where the structural failure is? You're putting a load which places the spar capstrips, or upper and lower surfaces of the spar undertension (beneath) and compression (above...what if the problem is exactly the opposite. What if the problem is a fatigue crack which will cause a wing failure...but won't shot up under the load you apply?
What if you put too much load on the structure and cause a weakness or a stress riser or create damage? Now you've become the defacto problem...not the wing, and you're not detecting, but introducing the problem. Suppose you're one of whom likes to push down on the horizontal stab of a 172 to lift the nosewheel and move it...or who helps turn it by pushing gently on the vertical stab, or the forward fairing. Suppose you're one of those who believes that you can't hurt a structure by operating the controls full deflection below Va, maneuvering speed. The problem is that you can...and Cessnas, especially 200 series Cessna's, are well known for the factory vertical stab attach brackets failing. I've discovered quite a number of them myself. You wouldn't hear the airplane making any noises. You wouldn't feel any give. But it's still broken.
I used to fly an airplane that got an enormous amount of maintenance attention. We had a program in place which stripped the paint on the lower surfaces of the wings regularly....once a week or more, and perfomed ultrasonic inspections. We crawled inside the wings to inspect them, and had a whole aproved maintenance program on it to back us up. Never the less, the wings came off the airplane, it caught fire in flight, and crashed, killing everyone. It had a good inspection program. Went through a full A check every day...but still came apart. Everyone on board was a qualified mechanic and inspector...with full tools and parts on board. The airplane got constant care...never the less, it crashed, and everyone died.
So, you're going to jack the DC8. Except where will you apply the load? On the center of the spar? Where? Yes, you can certainly damage an airplane by jacking it improperly...especially from a place where you ought not.