'thought these photos would be more of interest than it turned out. Failing any outside input, I think the spar grafting will hold.
When I build balsa spars from shorter lengths of stock, I diagonal the joint and use CyA, because it is much stronger than balsa and disperses/wicks into the balsa, spreading and tapering off the stiffness. So the extension of the joint and the dispersion of the glue make the joint very strong without concentrating the stress critically. I usually put the joint as far out on the half-span as possible.
'think this will work?...
Rebuilding a SkyRay that I demolished 12 years ago required reattaching spars and leading edge near the root. One spar was badly warped; so I grafted the broken end, which made a good fit with lots of surface area, to a new spar with a scarf joint. All were done with epoxy, since I wanted some gap filling for the l.e.and didn't expect penetration advantage from CA cement on the spruce spars. The scarf joints seem very strong. The leading edge had to be butt jointed, but I made 1/16" plywood laminates for the two flat sides and rely on the sheeting and rib to help unload that joint. I'll probably reinforce the l.e. with glass, but the silkspan should strengthen it. The last pictures must illustrate what's left, as I temporarily fit some ribs, because I forgot to take pictures of the jigged leading edge. The lamination technique is shown on a piece of 1/2" square stock that I was thinking of using as a replacement leading edge. If these repairs don't hold up, the loss is not so great. I can't re-paper the wing through the fuselage and should have left some silkspan on near it.