That looks great!

If you limit the flying to big, open, back and forth passes, there isn't that much stress. It's absorbing the vibrations and sending those bad vibes out the wing-tips, giving that junk the path of least resistance. I believe it works something like electricity, same goes for the shock waves of impacts.
I think applying some FG to the spar / rib intersections is worthwhile, and also to FG the ends of the spars to the perimeter of the frame. I just did a post mortem of an old DD and those areas were still mostly intact.