I had exactly the same thought
Yes, the tank skins are a tight fit on the tank ribs. I clecoed most of the bottom prepunched holes then I used some ratchet straps and blocks of wood on the aft side to help insert the ribs into the skin. Also used a scratch awl through the skin and rib prepunched holes to lever them into position to make it easier to insert adjacent clecos.
I wanted to bump this thread a bit because I am dealing with exactly the same situation that everyone else has. Aaron, you said you were going to contact Vans to discuss this but I don't believe I saw a response posted here. If there was one I would love to hear what they said.
I bought two new strap-only ratchets with no hooks and I plan to do the same thing and will post pics of my results. I had already filed and scotch brited my tank rib LEs to smooth out the bumps per Vans instructions, and I am satisfied that the rib flanges are the way that they need to be for a smooth fit.
I started on my left wing tank with the skin in the cradle. I found it easiest in my case to line up and cleco the top side of the ribs first, from LE to the rear. This went fine for all the ribs. Then I experienced no less than a 1/4 inch or more gap between the LE of the skin and the nose of reach rib. I immediately had the feeling that the tank skins were not bent as well as they should be. Personally I think this is a result from a combination of the way they are bent at the factory, and they way they are stacked together with all the other LE skins and highly compressed and taped together for shipping. Just a guess....
I too then tried my best at 11:00pm at night, after spending several hours prior to this on Z bracket prep and back drilling holes, to apply mass force with one hand on the rear flange of one rib, with a cleco in the cleco pliers at the ready in the other hand. While trying to insert the most forward cleco at the front of the LE edge skin, it was a "wonderful" feeling when I felt the cleco give way, scraping the skin for about 6 inches or so. I still have the vinyl on the exterior of the skin, but I know what I will find when I get enough courage to remove it to see how deep the scratches are. I said many choice words, threw the damaged cleco on the floor in disgust, and went to bed.
So I should have quit working before attempting this, because I was already tired. But you all know how it goes - why stop building when you are on a good roll, right?
Anyway, I could tell that the tank skin LE seemed to "want" to conform to the tank rib when I applied enough pressure by pushing up on the LE of the skin with one hand, and pushing down on the rib rear flange with the other. Problem is that I ran out of hands at that point, so I had none left to insert a cleco into a hole once they lined up.
So I have thought about this for a couple of days, then I found this post, and came to the same conclusion that ratchet straps should be able to wench down the ribs enough to line up the holes. I consider it a kind of reverse process from using them to wench the LE and tank assembly down on the main wing spar. This time you use them to force the tank ribs and skin to conform to each other and line up the rivet holes.
Now the only thing I need to consider is if I should try this with the skin in or out of the cradle. It definitely seems like the cradle is preventing the tank skin from forming around the rib, but I had no such problem with the outboard leading edge assemblies. They all went together in the cradle just fine, but were also a little tight the first time.
Wish me luck, and I'll report the results of the process with pics.
