I have just started construction of the left wing on the Sig LT-40.

I'm having a problem with the fit of the shear webs. They are too short to span from one rib to another. About 1/12" away from touching at each end. Would it be wise to add slivers of balsa in between the ends and the ribs to fill the gap?
If not, what do I do? It seems that they have shrunk.

Thanks for any help you can give.