As I feared, when I put the wing walk/root doubler on the OUTSIDE face of the wing skins, I could get the holes in the top surfaces to align, but all the holes underneath were a good 1/2" away from their mates in the lower skins and ribs.
So what to do...
Making an entirely new wing walk/doubler wasn't going to help since I'd run into the same problem all over again.
So I decided to cut away the leading edge of the root doubler (photo #2). I actually cut it back further than this photo so I wouldn't have to deal with the spring back of the leading edge bend. This left the doubler to work fine underneath the wing. It just wasn't going to work WITH the leading edge bend.
So I went to the polished (but abandoned) leading edge skin from my first failed attempt at a leading edge skin. I cut out an oversized section and placed it under the (now cut) root doubler, and used the pilot holes to mark holes in my doubler "patch" on the top surface, then cleco'd it in place (photo #3).
Then I wrapped the patch over the leading edge and held it in place with the same ratchet straps that I used to suck in the leading edge skin. Now I used the pilot holes in the leading edge skin at the UNDERSIDE of the skin to mark the holes in the patch. I took off the patch and drilled those holes.
Anyone who has built a Sonex will probably notice, but I don't think anyone else will once it's all polished up an has the gap seal installed at the fuselage.
I have NO IDEA how anyone makes the wing walk and doubler work as a single piece! The Sonex plans give no hints at all, and I didn't see any "how-to's" on any builder's web pages.
Beginning the doubler at the top surface.
I had to cut the doubler at the leading edge or it would never fit.