Yeap seems I learned that the hard way. Its interesting that in therory, reinforcing just a small section of an otherwise sound wing could actually cause it to fail.
Yup, or the other thing that I have seen happen is that there will be a failure point on a structure, so a brace/doubler is added, and the failure point just moves to the end of the brace/doubler. In the full size aviation world, the Citabria family had such an issue with the spar. An Airworthiness Directive was issue to addres the issue, and doublers were added/modified. Now there is anotherairworthiness directive to inspect the spar at the ends of those doubles as the crack location just moved. The best solution with those is similar to what you are doing, a completely different spar, in the Citabria case it is a new metal rather that wood spar.
Ireally like the "second" spar idea in you pictures. Like you mentioned, to keep the wing aligned using two piece ribs would be tricky. Besides, if you use one piece ribs, and then just make your shear webs so they fit nice and snug enough between each rib, the end result really won't be any weaker than the solid spar/split ribdesign. Especially with your carbon spar caps. This time around I doubt you will have any issues!!!