Thanks for all the replies.... I now get what everyone means by 'shear joint', and that one should NOT weld anything unless you want to go through a whole hell-of-a-lot of extra work fixing the metallurgy of the resulting part.
So far, the choices everyone has posted seem to boil down to: 1) Make new WAFs for one side using same-thickness strips of 4130, using the old ones as a template, then drill the main bolt-hole for the pin/attach-bolt based on where everything lines up. 2) Move the WAFs around on the spar, using dowels to plug the old bolt holes. My WAFs aren't really 'off' on the spar (both my old spar & my new wings are fully complete right now - the wings were slightly damaged in transit but nothing irreparable), and the holes appear to be the right diameter. So it would seem that making 'new ones' from strip steel would be the best choice, although I am open to more ideas.
